We have a Ruger P95, great gun, and easy to get in your price range. Couldn't go wrong with a Sig SP2022, Ruger SR9, S&W SD9VE either. If you want a 1911, you could probably get a basic RIA for $400ish. From what I hear, they work even if not up to Kimber or Wilson Combat standards.
Other option, to quote everyone else, used Glock.
Because I have one and love it and it's the least expensive, I'd say go P95. Very accurate, good reliability, fantastic trigger in my opinion.
If you want a striker fired, the SD9VEs look good, and the SR9 I played with at the LGS REALLY impressed me. Thin, great sights, the trigger was light and crisp.
Certainly couldn't go wrong with something that says "Sig" on the side either.
There are a lot of good deals to be found in the under $450 market, last I checked there's no law that says you have to buy an M&P, Glock, XD, CZ, Beretta, 1911, etc. You won't die in your sleep for buying a less expensive gun