Probably still the Cooler Master Hyper series, the 212+ or 212 Evo. If the 212+ is more than about $5 less the extra performance of the Evo doesn't justify the extra price.
If you are looking at water cooler you are looking at $50 minimum instead of $25-30 for the Hyper 212+/Evo which will give you similar performance. Frostytech has a nice chart that you can compare the performance of a large number of heatsinks with http://www.frostytech.com/articleview.cfm?articleid=276...
if you are looking for the best cooler for the money... its air not water cooling and the answer would be:
noctua nh-d14 or phantenks ph-tc14pe. both provide phenomenal cooling results for the money however are honkin huge! which could present some issues of its own.
if you wanted a water cooler (which isnt as budget friendly for the performance they give) i would suggest going with one of nzxt's kraken lineup such as the 140mm x60 or perhaps the corsair equivalent. those will provide decent performance at an okay price (when on sale!) but are still rather pricey. if you are satisfied with "okay" not "great" performance then have a look at corsairs 120mm cpu loop lineup.
i would suggest looking at some benchmark results for cpu temp and pick something from the list that suits your budget and also performs well.
on a side note the hyper 212+ and 212 evo coolers are overpriced and cheaper coolers with a similar 120mm fan design can have the same performance. the 212 evo is just found virtually everywhere which makes it easy to suggest due to availability. i have one myself and its better than the stock cooler but not stellar.
There is a better cpu cooler The Swiftec Polaris 120 . It cools as good as some of the best . It has 5, 8mm direct touch
copper heatpipes. It will cool Better Than the coolermaster Hyper 212 for sure. The problem is Availability. It Is 39.95 from Swiftec plus shipping . But from Jab Tech inc. it is currently $14.95 plus $12.00 or so shipping and some tax. I have run this on a 4.4 Ghz OC on an fx 8350 no problem. I am going to give it a try on an Fx 9590 with an upgraded Fan. But I have to say the hyper 212 gets a lot of marketing and is not to bad. It is highly available. There is also the EVGA 120mm acx cpu cooler on amazon. On hardware secrets website it was tested as the evga superclock cpu cooler. It beat out all other coolers they tested for a long time. It has 5 8mm direct touch heatpipes. It will set you back about $50.00 or so after tax with free shipping from Amazon. It will fit most mid towers. With tall ram you will have a problem with slot one maybe. with small ram it will cover slot one, but work. the same with the swiftec Polaris120. they are similar.