So far most posts have been either for a .22 or 38/357. .22's are indeed fun to shoot (and cheap ammo) however they require a heavy spring to set off the rim fire ammo. Therefore double action is hard to shoot accurately and can quickly tire out your trigger finger. Thus, most shooting tends to be in SA mode. If you get a .22, SA/DA is a must, not DAO. 38/357's will have a nicer trigger however the recoil will be much higher, especially in the lighter guns using 38+P or 357. After shooting 50 - 100 rounds your fingers/wrist can get sore which is no fun. So if you only want one gun that is fun to shoot all day you should consider one chambered in .327. Most of these guns can shoot .32 S&W, .32 S&W Longs, .32 ACP (all very low recoil) and .32 H&R Magnum and Federal .327 Magnums which have the energy to be good defensive rounds and still lower recoil than 38/357. The .327 is just below 357 magnums energy wise. The down side is ammo is harder to find and if your local store does not stock it you need to order it on line (and there's plenty available on line).