Glock 19. In my opinion, it's their best package of capacity (if you want to pony up for the standard-capacity mags), size, and shootability. Depending on where you live, you should EASILY be able to get one under $500. Mine would have been $459 retail, but I worked at the shop where I bought it at the time of purchase so I won't tell you what I actually paid.
I'd also toss in votes for the CZ-75 and the Ruger P95. I think the CZ is possibly the best overall value in handguns, period. The Ruger P95 would be toward the top as well. I can't point either of them naturally, so for me they aren't a good fit. The Glocks DO point for me, so I own a couple of them.
You just might find a used Beretta 92 in that price range. I don't like them, but it might work for you.
Bob's Standard Advice: Try several different models. Rent them or borrow them from friends, but shoot as many different ones that fit your criteria as you can before you make up your mind. I personally don't buy a gun just to "try it out", and then trade it for something else later. You almost always end up costing yourself money by going that route.
If you want something that's new, and that is top shelf, you're probably limited to Glock, Ruger, and CZ. In my opinion, that's not a bad thing at all.