Ambipom got a new toy in gen 5, Switcheroo. I found that to be very useful on a Choice Band set and I've had some very good success with it:
Ambipom (F) @ Choice Band
Trait: Technician
EVs: 252 Atk / 4 SDef / 252 Spd
Jolly Nature (+Spe, -Spd)
- Double Hit
- Fake Out
- Switcheroo
- U-turn / Pursuit
Double Hit will be the main move to be used, boosted by Choice Band, Technician and STAB and being able to hit through Substitute makes it a very useful and powerful move. Fake Out makes a good revenge killing move but it will turn Ambipom into set up fodder so you have to be careful with that. Switcheroo allows Ambipom to screw over physical walls that can take it's hits with ease. U-turn is for scouting (it will still deal ~50% ot a defensive Tyranitar). There are other moves that could be used over U-turn though, most notable Pursuit. Ambipom outspeed most Ghosts anyway and via Pursuit he can trap them completely.
This set is great to be used with other physical attackers, as Ambipom lures out their common counter and cripple it with Switcheroo or weaken it enough. It can also be used as a lead, a hit and run pokemon or as a late game sweeper.

Ambipom (F) @ Choice Band
Trait: Technician
EVs: 252 Atk / 4 SDef / 252 Spd
Jolly Nature (+Spe, -Spd)
- Double Hit
- Fake Out
- Switcheroo
- U-turn / Pursuit
Double Hit will be the main move to be used, boosted by Choice Band, Technician and STAB and being able to hit through Substitute makes it a very useful and powerful move. Fake Out makes a good revenge killing move but it will turn Ambipom into set up fodder so you have to be careful with that. Switcheroo allows Ambipom to screw over physical walls that can take it's hits with ease. U-turn is for scouting (it will still deal ~50% ot a defensive Tyranitar). There are other moves that could be used over U-turn though, most notable Pursuit. Ambipom outspeed most Ghosts anyway and via Pursuit he can trap them completely.
This set is great to be used with other physical attackers, as Ambipom lures out their common counter and cripple it with Switcheroo or weaken it enough. It can also be used as a lead, a hit and run pokemon or as a late game sweeper.