I would suggest the Arctic Freezer 7, it works great. Just make sure your case has room for whatever you buy because aftermarket hs/f are way bigger than stock ones.
If you are on a budget, pick one of the ones nickm926 said, if you want the absolute best air cooler get a Thermalright ultra-120 extreme with a good fan. You wont be disappointed.
Slightly more expensive tho and not as many ratings as the one suggested above. Is fitting into the case going to be a problem for Newegg.com - ARCTIC COOLING Freezer 7 Pro 92mm CPU Cooler - Retail and it looks like if it does fit then it will blow directly into my case fan - will that be a problem for flow for the rest of the case or help it?
My case is:
COOLER MASTER CAV-T01-WKA
(A coolermaster mid tower)