I would get the rc-n3 or the rc-c3 from DX or if u want to spend a little more get a q5 version from shiningbeam.com, as far as cr123 lights go. The rc-c3 is a single rc123 light and is a little cheaper and the rc-n3 is a great light can use either 1 cr123 or two AA's, it comes with an extension tube. The Q5 versions can put out quite a bit of light, or so I hear.
The Buckle Im pretty sure the cheapest/ brightest aaa light.
For a single AA light that is cheap and bright the rc-g2 is pretty good, again shiningbeam sells a slightly more expensive q5 version.
Although, I think if you are only getting one you should probably get the q5 rc-n3. It gives you the option of the rc123 which will be brighter than anythign a aa or aaa can muster plus you still have the option of using it in 2xAA mode. Also romisen is a pretty respectable brand, as far as budget lights go they are very solid. Plus it has a Glow in the Dark tail cap that I really like