I like a prop. Something to fidget or play with while sitting around, when I'm forced to sit around.
Often times that involves a knife because I've always got one on me. I'd also be content tossing a ball lightly overhead, twirling a stick, flipping a coin, etc.
I don't like objects that make a lot of noise. Autos almost always make too much noise to fidget with, as do assisted knives. I also don't like things that get uncomfortable after a while. Some knives have thumbstuds that start to hurt your thumb.
I think my favorite knives to fidget with are Spyderco framelocks like the Sage 2 and the Ti Military. They're quiet and comfortable. My ZT 0850 is also nice.
I love the feel of a compression lock, like the pm2, but have never found the knife itself all that compelling. They're fun to play with for a bit, then I sell them. I've basically written the pm2 off at this point. Its a great knife... for someone else.
All that said... at the point where your fidgeting is annoying your wife or whomever you've probably wasted enough time. Go find something to do. Like post about fidgeting here