One I owned and can reccomend: The LCP is an awesome carry gun, almost regret getting rid of mine, but 380 ammo is just too expensive and I needed fewer calibers I had to buy just to go shooting. I then used my LC9 as my carry, but I later realized I didn't want such a large caliber to use for defensive purposes so I got rid of it, almost regret as well. Both were really nice firearms, accurate, fun to shoot and very concealable.
Others have mentioned some very good options as well. Here's my list and why...
1st - Sig P238, lifelong quality, 1911 platform, concealable, SA
2nd - Ruger LCP, extremely concealable, great experience with
3rd - S&W Bodyguard, concealable
4th - Bersa Thunder, lifelong quality, DA/SA
Even considering price/value the Sig wins, simply because it's the only single action up there. Until proven otherwise, I believe the polymers too will stand the test of time, but I'm firmly anti-DAO. The Bersa is an amazing quality piece, but far too large for what I consider concealable, as I'm a pocket carry only type. There are other options like the Colt mentioned and several I'm not thinking of right now, but these are the ones I've either owned or considered.