252 HP/4 SpA/252 Spe
A different set, this Siglyph uses Dual Screens and its nice support moves to aid sweepers. Tailwind can help a slower attacker net a few kills, while Gravity allows things like Starmie to wreak havoc with Hydro Pump and Thunder. Thunder Wave paralyzes a pokemon. Thunder Wave is better if you would rather cripple a pokemon for the game, but Tailwind is better if you want to sweep straightaway. The final slot is so you're not Taunt bait, but Will-O-Wisp is viable to cripple things like Tyranitar.
Ability: Magic Guard/Tinted Lens
Item: Life Orb/Choice Specs
-Ice Beam/Shadow Ball
-Hidden Power [Fighting]/Shadow Ball
Most of this set depends on what ability and item you use. Choice Specs and Tinted Lens allows Siglyph blast through Steels and Dark types with its STABs. Life Orb and Tinted Lens gives recoil, but you don't need to switch, which means less Stealth Rock damage. Life Orb and Magic Guard give less power, but it gains the ability to change moves and negates SR weakness and Life Orb recoil. This set works better in lower tiers, so it might be better to run Shadow Ball over Ice Beam, since Dragons are less of a threat and Grass types are handled by Air Slash.