I prefer semiautomatic guns, but that's because I'm scrupulous about maintenance. If I wanted a gun I could take out of the drawer 6 months later with no doubt that it would fire, I'd choose a quality .357 Magnum or .38 Special revolver from Smith & Wesson or Ruger. My top choices would be the Ruger GP100 4", Smith & Wesson 686 4", Ruger SP101 3", Smith & Wesson Model 60, Ruger LCR, and Smith & Wesson 642, in descending order of size.
My grandpa's old Colt Python isn't a safe gun, we shoot it and my dad tucks it under his truck seat on long trips, and sometimes it does nightstand duty. Every time I take that gun out of its leather it so obviously is ready for action. Revolvers give you a great deal of confidence in their steadfastness.
Beretta PX4; 92FS; 92S; 8040G | Sig Sauer SP2022; P6 | Colt Python 4"; 1968 Detective Special 2"| Smith & Wesson M642 No-Lock | Ruger LCP; 10/22 | Daniel Defense M4V1 | Remington 870 | Alpine M1 Carbine | Steyr M1895 |1943 Izhevsk Mosin M91/30 | Walther PPS