Well, if we're talking about the one that we would LOVE to own, but don't, I would say a model 66 NO DASH with the stainless rear sight and a 4 inch barrel.
If we're talking about the one we would LOVE to own, but probably NEVER WILL, I'd hafta say a PRE model 27 with a three and a half inch snout.
If we're talking about the one that we DO own and would never part with, it would be a toss up between my dad's old Victory model 4 inch M&P or my current EDC/BUG, my Smith & Wessom J frame model 38 Airweight "Bodyguard" from 1985. It's in my pocket everytime I'm vertical in a DeSantis "Nemesis" pocket holster...
Every. Single. Day.