I have this little Streamlight Microstream:
http://www.amazon.com/Streamlight-66318-...422&sr=8-10It meets all your criteria except it has a pushbutton switch.
It is $16 shipped. It is very bright, simple, and rugged.
I really trust the Streamlight brand, which makes some very high-end tactical lights. I also have a larger Streamlight Strion LED, which also happens to be what the city cops here carry.
I also have the Arc AAA, which according to their site is still made, and is about $30. It is a bit shorter, has a twist switch, but is nowhere near as bright. I had one that I had some trouble with, that they fixed no problem.
David