One pistol- I'd have to choose my Walther p-38. I've shot almost a thousand rounds through it so far and nat a single malfunction. May only carry 8 rds. but ifyou're a good shot, you don't really need any more.
The Ruger BlackHawk SA Revolver with 7.5 in. barrel was my first handgun choice. Like others have commented it can fire .357MAG and .38SPL rounds. Super accurate for target shooting. Great stopping power for self defense. I find it cheaper to shoot than Semi-Auto Pistols because you don't have the option to rapid fire $5.00 worth of ammo in less than 10 seconds. My first purchase was a Guns & Ammo Annual Magazine. It lists a wide range of pistols & rifles with great manufacturer spec. and pricing for at home comparisons without salesman pressure. Whatever your first choice is puchase alot of ammo, find a good shooting range and practice, practice, practice.