Since everyone seems to be suggesting the same thing, I'm gonna introduce my Starmie, which I got with help from Aragornbird ages ago
Starmie@Leftovers
EVs: 212 HP, 58 Sp Atk, 240 Spd
-Surf
-Thunderbolt/Thunder
-Recover
-Rapid Spin
Starmie can survive a couple of neutral hits, but don't start trying to wall anything with her
Thunderbolt has more accuracy than Thunder, but I use it on my Rain Dance team so I have Thunder for more power.
That's the more bulky Starmie, not the pure special sweeper. I pointed out in my thread that Starmie has a rather boring 100 base Special Attack, but her defenses are high enough for her to pull off "bulky water". This turns her into the greatest counter for Infernape and Blaziken (she resists both STABs they have).
A Pure Special Sweeper is as follows:
Starmie @ Petaya Berry/Leftovers/Choice Specs
Timid Nature
EVs: 252 SpAtk, 252 Speed, 6 HP
- Surf
- Thunderbolt
- Ice Beam
- Grass Knot/Psychic/Rapid Spin
Rapid Spin works well on Starmie since people will usually always switch to a counter (like Blissey, although I would much prefer using that as a chance to catch Blissey on a switch in), so it's almost always fool-proof. Grass Knot is helpful to take out Swampert (who otherwise takes less than 50% from Surf), and it does more damage to Milotic than Thunderbolt. Psychic is also good, since it OHKOs Gengar (and people always seem to think Gengar is faster than Starmie), and also gives her a move against Heracross (although beating him to the punch is rather hard with the Scarf Cross running rampant). Really, the move can depend on the rest of your team... if you have Swampert trouble like myself, Grass Knot can solve it. If Gengar and Heracross scare you, Psychic is the way to go. If you need a Rapid Spinner, she does that well too.
However, be careful with what you switch her into... she may be bulky, but she can't take too many hard hits.
