Usually Russian Makarov in .380
Well, as much as I like real firearms (for handguns, that means "it starts with a '4' in caliber) I can't always conceal a full sized auto like a 1911 or a full sized N-frame. So..... figuring that even a small gun is better than no gun, I carry my Russian Mak in .380 more than anything else. I've been surprised over the years how durable, reliable, and even how accurate it is. Paired with premium ammo, it's better than just leaving a .45 at home.