This is difficult for me as I love revolvers. That said, I would take my Star MOD 30MI. It's built like a tank (all heavy steel,) holds 15+1 rounds of 9MM and it has never jammed on me once.
But, if this wasn't a handgun thread, I go for a utility rifle. My Paratrooper SKS is rugged, handy & simple enough to keep functional without any outside support.