A J frame or Ruger LCR if you want a revolver, or one of the small pocket rockets(32acp or 380) in your pocket. I like my KelTec P32. It is perfectly reliable, has a last shot hold open, carries 7+1 or 10+1, and weighs 6oz unloaded. Its easy to control(as opposed to the tiny 380s) and I can get follow up shots on target easily and quickly. Dont let the Big Boom Guys tell you the 32acp is crap. It might not be as capable as some other cartridges to make a one shot stop, but believe me, 11 shots of 32acp will stop anything.
My P32 with 10 shot magazine and TR1 Armalaser...
7 shot magazine