EDIT: CM Blissey > Starmie.
Infernape @ Focus Sash
Ability: Blaze
Nature: Naive (+Spe, -SpD)
EV: 4 Atk / 252 SpA / 252 Spe
-Fake Out
-Close Combat
-U-Turn
-Overheat
Works nicely as a starter. Fake Out destroys Focus Sashes, while Overheat and Close Combat put things in pain. U-Turn works especially well with Close Combat and Overheat, as they both have side effects that make you want to switch. Focus Sash guarantees I survive an attack, unless they have Focus Sash Fake Out Ambipom.
Blissey @ Leftovers
Ability: Serene Grace or Natural Cure
Nature: Modest (+SpA, -Atk) or Bold (+Def, -Atk)
EV: 4 HP / 252 Def / 252 SpA
-Calm Mind
-Thunderbolt
-Ice Beam
-Softboiled
Blissey is very good at getting a couple free boosts after Infernape has U-Turned out of a special threat such as Milotic. It can probably sweep many of the battle tower teams, as I rarely see extremely powerful physical moves, barring EQ, which it survives easily. I have a Modest Happiny that I got from the man in Hearthrome, which has near perfect IVs :), but it has Serene Grace. I bred a Bold one from it that also has great IVs, but it has Natural Cure. Either one would work, but I am probably sticking to Modest because it is great to randomly freeze or paralyze something. A 1 in 5 chance isn't bad at all.
Garchomp @ Yache Berry
Ability: Sand Veil
Nature: Jolly (+Spe, -SpA)
EV: 4 HP / 252 Atk / 252 Spe
-Swords Dance
-Outrage
-Earthquake
-Fire Fang
Well Garchomp may be banned on Shoddy battle but I can still use it in Battle Tower :) I think you all realize how lethal this thing is, but he helps revenge kill and sweep at the same time. Yache Berry for those random ice attacks from things like Rhyperior :)
Strategy: There isn't a unison strategy here, just 3 excellent sweepers. I find that my prediction often prevails over a good strategy, as with only 3 pokemon, it is tough to find the time to set up such strategy. BTW, this is NOT for the wifi battle tower, better yet the local.

Infernape @ Focus Sash
Ability: Blaze
Nature: Naive (+Spe, -SpD)
EV: 4 Atk / 252 SpA / 252 Spe
-Fake Out
-Close Combat
-U-Turn
-Overheat
Works nicely as a starter. Fake Out destroys Focus Sashes, while Overheat and Close Combat put things in pain. U-Turn works especially well with Close Combat and Overheat, as they both have side effects that make you want to switch. Focus Sash guarantees I survive an attack, unless they have Focus Sash Fake Out Ambipom.

Blissey @ Leftovers
Ability: Serene Grace or Natural Cure
Nature: Modest (+SpA, -Atk) or Bold (+Def, -Atk)
EV: 4 HP / 252 Def / 252 SpA
-Calm Mind
-Thunderbolt
-Ice Beam
-Softboiled
Blissey is very good at getting a couple free boosts after Infernape has U-Turned out of a special threat such as Milotic. It can probably sweep many of the battle tower teams, as I rarely see extremely powerful physical moves, barring EQ, which it survives easily. I have a Modest Happiny that I got from the man in Hearthrome, which has near perfect IVs :), but it has Serene Grace. I bred a Bold one from it that also has great IVs, but it has Natural Cure. Either one would work, but I am probably sticking to Modest because it is great to randomly freeze or paralyze something. A 1 in 5 chance isn't bad at all.

Garchomp @ Yache Berry
Ability: Sand Veil
Nature: Jolly (+Spe, -SpA)
EV: 4 HP / 252 Atk / 252 Spe
-Swords Dance
-Outrage
-Earthquake
-Fire Fang
Well Garchomp may be banned on Shoddy battle but I can still use it in Battle Tower :) I think you all realize how lethal this thing is, but he helps revenge kill and sweep at the same time. Yache Berry for those random ice attacks from things like Rhyperior :)
Strategy: There isn't a unison strategy here, just 3 excellent sweepers. I find that my prediction often prevails over a good strategy, as with only 3 pokemon, it is tough to find the time to set up such strategy. BTW, this is NOT for the wifi battle tower, better yet the local.