I'm currently playing a swashbuckler/fighter (2/2). Going to multiclass into duelist once my BAB is high enough, stay there until my duelist levels equal my Int bonus (+4) for the AC modifier, and then I'll switch back to swashbuckler/fighter for the rest of my career.
A lot of my feats are from the PHB II, but basically they will allow me to make multiple attacks, even attack multiple opponents, during a spring attack.