I've had a lot of success with this one as my lead.
Ambipom @ Life Orb / Silk Scarf / Muscle Band
252 Atk / 252 Spe / 4 HP
- Fake Out
- Ankle Sweep / Low Kick
- U-turn / Pursuit
- Return / Taunt / Pursuit
Obviously, if you're running Return, the Silk Scarf is the way to go. This works great as an anti-lead, and again for late-game damage if you just want to come in and smack something with priority. Not everyone expects Taunt on Ambipom surprisingly, but the real magic of this set is Ankle Sweep--not only does it have 90BP with Technician, but it also lowers the foe's speed. Using it against faster, frail opponents that fail to KO you/switch in can often force them to switch out or risk being KO'd by the now-faster Ambipom. U-Turn works perfectly with this, allowing you to scout any switches that come after Ankle Sweep.
The set lacks a little bit of raw power, which is why Life Orb is the suggested held item. Unfortunately, throwing out Fake Outs and U-Turns is going to cause recoil damage to build up really fast, so the Silk Scarf (if using Return) or even the Muscle Band (if using Pursuit / Taunt) give you just a wee bit of a boost without having to deal with constant loss of health. Or if you have Item Clause and want Life Orb on something else.
It's also worth noting that if you don't pack a Life Orb, you miss out on 2HKOing 64 HP/0 Def Infernape Leads with Fake Out and Ankle Sweep, and the guaranteed OHKO on 0 HP/4 Def Lucario with Ankle Sweep. You also lose the ability to OHKO 252 HP/0 Def Tyranitar with Ankle Sweep (however, Low Kick is still a guaranteed OHKO, even with a Silk Scarf).
Worked well for me.