Originally Posted by mpw94
I would further suggest an E8400, E8500 or E8600 of any revision are still good. It will make a fast work computer too as long as you're not really playing games.
An E5200 was a good clocker in the day too, so were the E2140's, E2160, E2180. I assume the E5400 etc were also good. Socket 775 was probably one of the best Intel sockets to overclock, that and Sandy Bridge stuff, Ivy/Haswell just have too much heat and are too new for what you want. If you can grab a 2500k cheap you can find a cheap P67 board somewhere too
EDIT: P55 is good too, like an i3 or even an i5 on that socket would be great too.