Anti Lead
An anti lead is a lead that is made to beat most, if not all common leads. In a lead situation we see vistory out of who can get their job done. An anti lead's job is to stop the opposing lead getting its job done.
Thunderus is an excellent anti lead. With its ability "Prankster" it can taunt even the fastest of Suicide Leads and has move pool enough to KO or cripple other common leads.
EX

Thundurus (M) @ Life Orb
Trait: Prankster
EVs: 4 Def / 252 SAtk / 252 Spd
Timid Nature (+Spd, -Atk)
- Taunt
- Thunderbolt
- Focus Blast
- Thunder Wave
Attacking Lead
An Attacking lead is a Pokémon that works in the lead position, however instead of setting up, it will generally just outright attack.
Machamp makes a great attacking lead, as it has a disruptive move in Dynamic punch, and enough bulk to generally 2HKO the opponent's lead before it falls itself.
Ex:

Machamp (M) @ Lum Berry
Trait: No Guard
EVs: 240 HP / 252 Atk / 16 Spd
Adamant Nature
- DynamicPunch
- Payback
- Bullet Punch
- Substitute / Stone Edge
Glass Cannon
A glass cannon is pretty much what it sounds like. It's a pokémon that can hit incredibly hard (Cannon) with very poor defences (glass).
Gengar, whilst some running tankish support sets, are generally perceived as Glass Cannons, with 130 Special Attack, but a very low 60 Defence.
EX

Gengar (M) @ Life Orb
Trait: Levitate
EVs: 252 SAtk / 4 SDef / 252 Spd
Timid Nature (+Spd, -Atk)
- Protect
- Hidden Power [Fire]
- Focus Blast
- Shadow Ball
Lure
A lure is a pokémon whose sole purpose is to bait a pokémon into play and beat it. The idea is to lure a pokémon in that counters your main sweeper.
Jirachi can be a great lure, as it can feign a multitude of sets, thus making the pokémon its luring in feel safe enough to switch in; only to be OHKOd for doing so. In the Example, Jirachi Feigns a Scarfed set by using the moves Iron Head and U turn until Either Scizor or Gliscor switch in.
EX:
Gliscor / Scizor Lure

Jirachi @ Expert Belt
Trait: Serene Grace
EVs: 252 Atk / 4 SAtk / 252 Spd
Naive Nature (+Spd, -SDef)
- Iron Head
- Fire Punch
- Hidden Power [Ice]
- U-turn
Mixed-Sweeper
A mixed sweeper is a pokémon that can attack from sides of the attacking spectrum. Using its dual high attacking stats to its benefit, being able to get passed most walls by hitting them where they are vulnerable. This is what people mean when they refer to "MixMence", or "MixApe."
Infernape is a prime example of a mixed sweeper, with access to a multitude of moves from both sides of the spectrum, with reasonably high 104 in both offencive stats.
EX:

Infernape (M) @ Life Orb
Trait: Blaze
EVs: 64 Atk / 252 SAtk / 192 Spd
Modest Nature (+SAtk, -Atk)
- Close Combat
- Fire Blast
- Hidden Power [Ice] / Nasty Plot
- Grass Knot / Nasty Plot
Phazer / Pseudo Hazer
A Pseudo Hazer is a pokémon that uses moves like Roar or Dragon Tail, or Perish Song to cause a pokemon to switch. This in turn makes the switched pokemon lose their stat boosts, which is what the move "Haze" does.
Skarmory is a brilliant Pseudo Hazer, with a huge Defence stat and access to Whirlwind / Roar it can easily come in on boosting Physical Attackers and Phaze them out.
EX:

Skarmory (M) @ Leftovers / Shed Shell
Trait: Sturdy
EVs: 252 HP / 252 Def / 4 Spd
Impish Nature (+Def, -SAtk)
- Brave Bird / Drill Peck
- Spikes / Stealth Rock
- Whirlwind
- Roost
Physical Sweeper
A Physical sweeper is a Pokémon that uses only physically based moves to sweep. They generally use Swords Dance, Bulk up or Dragon Dance to boost their Attack stats further.
Terrakion is a brutal Physical Sweeper, with a high Attack stat of 129, access to Swords dance and a 108 base speed. It can also boost its speed with Rock Polish, or save itself from being Phazed with Taunt. Not only that, but it arguably has the best Dual STAB in the game.
EX:

Terrakion @ Life Orb
Trait: Justified
EVs: 40 HP / 252 Atk / 216 Spd
Adamant Nature (+Atk, -SAtk)
- Swords Dance
- Rock Polish / Taunt
- Close Combat
- Stone Edge
Pseudo Passer / Dual Screener
These are pokémon that use moves like Reflect, Light Screen and Wish with the intent to support the next pokémon to switch in. These pokémon are generally found holding Light Clay
Espeon makes a fine Pseudo Passer, with access to Reflect, Light Screen and an ability that stops it from being taunted (Magic Bounce).
Ex:

Espeon (F) @ Light Clay
Trait: Magic Bounce
EVs: 252 HP / 4 SAtk / 252 Spd
Timid Nature (+Spd, -Atk)
- Reflect
- Light Screen
- Psychic
- Hidden Power [Fighting]
Spin-Blocker
A spin blocker is a Ghost typed pokémon whose function is to switch in on Rapid spin, a normal typed move that removes Entry Hazards.
Spiritomb makes a great Spin Blocker, with its reasonable bulk and a movepool that can outright OHKO or cripple the common rapid spinners.
EX:

Spiritomb (M) @ Expert Belt
Trait: Pressure
EVs: 248 HP / 152 Atk / 108 SAtk
Brave Nature (+Atk, -Spd)
- Will-O-Wisp
- Pursuit
- Hidden Power [Fighting]
- Sucker Punch
Spinner
A Spinner, or rapid spinner, is a pokémon whose purpose is to remove entry hazards as to support its team. For instance, if a team is running Charizard, who takes 50% from Switching into Stealth Rock, it is best to have a rapid spinner to support it.
Hitmontop is a great Rapid Spinner, as it can beat most Spin Blockers with sucker punch (or Foresight + Fighting Move) and then proceed to Rapid Spin anyway.
Ex:

Hitmontop (M) @ Life Orb
Trait: Technician
EVs: 240 HP / 248 Atk / 20 Spd
Adamant Nature (+Atk, -SAtk)
- Fake Out
- Mach Punch
- Rapid Spin
- Sucker Punch
Revenge Killer / Trapper
A Revenge Killer or Trapper, is a Pokémon designed to come in once a pokémon has fainted, and then defeat the opposing pokémon in revenge. Trapping refers to putting a Pokémon in a position that damns them regardless of what they do, via the usage of moves like Pursuit or abilities like Shadow Tag.
Tyranitar is one of the Best Trappers / Revenge Killers, as it can out speed a multitude of Pokémon and hit them incredibly hard, it also has access to Pursuit to function as a great trapper, too.
EX:

Tyranitar (M) @ Choice Scarf
Trait: Sand Stream
EVs: 252 Atk / 4 Def / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Pursuit
- Stone Edge
- Crunch / Earthquake
- Fire Punch / Aqua Tail / Fire Blast / Ice Beam
Special Sweeper
A Specially sweeper is the polar opposite to a physical Sweeper, using its special attacks to sweep the opponent. They usually use Calm Mind, Quiver Dance or Nasty Plot to Further Bolster their Special Attack.
Latios is a Prime example of a Special Sweeper, with 130 Base Special Attack, 110 Speed awesome typing and access to Calm Mind
EX:

Latios (M) @ Life Orb
Trait: Levitate
EVs: 252 SAtk / 4 SDef / 252 Spd
Timid Nature (+Spd, -Atk)
- Calm Mind
- Dragon Pulse
- Psyshock / Surf
- Hidden Power [Fire]
Stall Breaker
Not to be confused with a wall breaker, its function is to make a stall team or defencive core crack by putting pressure on it and using moves that make the core function outside of its optimal strategy.
Gliscor is one of the best Stall breakers with Access to Taunt and Roost, an ability that makes it impervious to status conditions (poison heal), not to mention its great resistances/immunities, great STAB type and a high speed.
EX:

Gliscor (M) @ Toxic Orb
Trait: Poison Heal
EVs: 252 HP / 40 Def / 216 Spd
Jolly Nature (+Spd, -SAtk)
- Taunt / Fling
- Protect
- Earthquake
- Ice Fang / Facade / Acrobatics
Status Absorber
A status absorber is a Pokémon that can do pretty much what the title suggests, take statuses with impunity or in some way benefit from them, be that with Natural Cure, Guts or running a Rest Talk set.
Shaymin makes a great Status Absorber, being able to switch in to the likes of Blissey, take the status and start using Seed Flare to wear Blissey down. It can then use rest to bring itself to full HP and switch out and lose its sleeping status, thanks to Natural Cure.
EX:

Shaymin @ Life Orb
Trait: Natural Cure
EVs: 40 HP / 248 SAtk / 220 Spd
Timid Nature (+Spd, -Atk)
- Seed Flare
- Earth Power
- Hidden Power [Ice / Fire]
- Rest
Status Platform
A status platform is a Pokémon with a move-pool full of status inducing moves like Thunder Wave and Spore.
Butterfree can function as a great Status Platform with access to all of the Status Powders and the ability Compound eyes to boost their accuracy.
EX

Butterfree (M) @ Choice Scarf
Trait: Compoundeyes
EVs: 248 HP / 8 Def / 252 Spd
Timid Nature (+Spd, -Atk)
- Sleep Powder
- Stun Spore
- U-turn
- Bug Buzz
Suicide Lead
A suicide lead is a Pokémon that says "to hell with sweeping, I'm a just set up real quick." They are usually fast pokémon with access to Spikes, Stealth rock and or taunt. They have one goal; set up as fast as possible.
With base 130 speed, access to Taunt, stealth rock and Quake Edge, Aerodactyl is one of the best Suicide leads, as it can stop the opponent setting up, set itself up and then dent something on the way down.
EX:

Aerodactyl (M) @ Focus Sash
Trait: Pressure
EVs: 252 Atk / 4 Def / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Stealth Rock
- Taunt
- Stone Edge
- Earthquake
Tank
A tank is pokémon that is made to successfully take hits through the duration of the match, but isn't necessarily required to do so through the duration of the match. The key difference between a tank and a Wall is that a tank generally speaking won't have a reliable way of recovery.
Ferrothorn is a great example of a tank, it has support options enough to support the whole team, it can live hits with its beastly defences and hit really quite hard on its intended targets
EX:

Ferrothorn (M) @ Leftovers
Trait: Iron Barbs
EVs: 252 HP / 4 Atk / 252 SDef
Impish Nature (+Def, -SAtk)
- Stealth Rock / Spikes
- Leech Seed / Spikes
- Thunder Wave / Gyro Ball
- Power Whip
Wall
A Wall is a pokémon who does exceptionally well over the duration of the match and is intended to do so over the duration of the match. It will almost always have a means of recovery, be it Roost, Softboiled, Recover or Wish. With access to instant recovery moves (recover et al) or a reliable form of recovery (wish + Protect) walls by default have the ability to stall out the Pokémon they intend to wall.
Porygon-2 can make an extremely potent wall in Gen-V with the newly added eviolite item, which boosts both the Special and Physical Defence of a Pokémon. It also has access to Potentially crippling moves like Thunder Wave and recover to ensure it is consistent over the duration of the match.
EX:

Porygon2 @ Eviolite
Trait: Trace
EVs: 252 HP / 4 Def / 252 SAtk
Modest Nature (+SAtk, -Atk)
- Toxic / Trick Room / Thunder Wave / Tri Atack
- Recover
- Ice Beam
- Thunderbolt
Wall Breaker
A wall breaker is pokemon focused on consistently breaking walls rather than sweeping. A wall breaker will generally use both sides of the Attacking Spectrum, using extra powerful moves to ensure OHKOs on the intended walls.
Dragonite is an exceptional Wall Breaker, with access to extremely potent attacks that are super effective against a lot of common walls.
EX:

Dragonite (M) @ Life Orb
Trait: Inner Focus
EVs: 252 Atk / 252 SAtk / 4 Spd
Quiet Nature (+SAtk, -Spd)
- ExtremeSpeed
- Draco Meteor
- Fire Blast
- Superpower