nothing really decent for $50. All the headsets under $100 are crappy. You're better off getting a good set of headphones (no mic) and using a seperate mic.
Sennheiser HD201 ($41 www.headphones.com.au ) and a clip on mic maybe?
if you can stretch your budget the beyerdynamic DT234pro is only headset i'd recommend (they don't look as aesthetically pleasing as the ZOMGWTFPROGAMER type 'phones but they are a nice all rounder)
http://headphones.com.au/psingle?productID=16Theres also the steelsound ones but they are a bit of a rip unless you are a competitive gamer (in which case there are better choices anyway). harsh and unforgiving they only work for FPS games. Listening to music on them would be comparible to using nightvision goggles during the day - useless.
http://headphones.com.au/psingle?productID=344Some people will think that you're bonkers for paying more then 20cents for a pair of headphones but they are worth it imo. Personally i use a set of headphones that are $300 and i love them.