Impossible to pick one. However, I will list three of the guns in my modest collection and I mean modest compared to the virtual armories posted in this thread
and yes, I will just admit it, I'm JEALOUS
-- heck, I don't think I could afford the obligatory Safes to secure those beauties...
My 92, 1911 and Hi Power. The thing that for me seperates these from my other handguns is that they fit my hand like a glove and I am more (easily) accurate with them as though it's second nature-like. Essentially, they make me look much better at shooting than I actually am compared to same shooting sessions say with my Ruger P95 or Taurus 24/7 OSS.