Most underrated Gen III Pokemon?

[Jirachi Dude]

Banette. It has pretty good attack and ok speed, so when I restart my sapphire, I am definitely going to use one of those.

[AmbipomMaster]

I want to say the must underrated Gen III Pokemon is Grumpig. I've never, in all of my years of playing Pokemon, seen someone use it. I trained one in Ruby and it was a great Pokemon!

You've met one now! Grumpig is my favorite Psychic type! I'm in fact going to use one in my Emerald run before the X and Y release.

[Palamon]

Surskit. That Pokemon does have potential and whatnot. It's easy to use and its typing is interesting. It has more potential when it becomes Masquerane but still.

[Shymain]

When people saw my Shiftry, they were like: 'Dude, really? That weird thing?’ Ironically, Shiftry is a cool, fast and hard-hitting Pokè (IMO).

[Greekboy]

Banette (might of spelled it wrong), turned out to be one of my strongest Pokemon in gen 3 once it had evolved from shuppet

This...
I used it in my recent Sapphire run, and it swamped both the Tate + Lisa gym (a lot lower leveled, too) as well as the fight vs Phoebe..
It has its flaws, but it can be a really good pokemon (maybe a little faster to pay up for that bad defence? :P)

[Chaser26]

Not sure if anyone has mentioned Xatu yet, but I wouldn't be surprised. After playing through Red Rescue Team the first time, I was alerted to the fact that Xatu was a pretty interesting Pokemon. Later on in my Emerald, I decided to catch a Natu in the safari zone and train it a bit, just to fill my sixth slot. However, as it evolved, and eventually got to level 65 and learned Psychic, it became an odd staple in all of my future playthroughs.

[The DragonKnight]

Manectric. I love it's design, but it is never talked about. It was also pretty damn awesome in XD GoD, him and Lugua were my two biggest assets.