Nice coolers sorted by price:
Cooler Master Hyper 212 Plus - $30 (use this myself, CPU never goes over 50°C heavily OC'd)
Scythe Ninja 3 - $50
Thermaltake Fio - $58
Cooler Master V8 - $60
Thermalright Venomous X - $75
Noctua NH-D14 - $85
If I was you, I'd either get Hyper 212+ (best bang for the buck) or Noctua NH-D14 (simply the best air cooler out there). A good compromise between those two could be Scythe Ninja 3, if D14 is too expensive for you.
Don't get those crappy watercooling kits tho - they perform worse than most of air coolers I listed, and they're overpriced. If watercooling is used, it should be used right - with proper pump, proper rad, proper fans etc.
Same goes to tire-looking Zalman's CPU coolers - they were good. Aren't anymore.