Although I am getting an M4 I would recommend the G36c. I don't like the look of the standard G36 nor the K variant but the c carry handle gives a totally different look to the G36. Also, like LUTNIT said, the G36c can be fitted with a large handguard which would be the first thing I would change on it.
TM G36c with Large handguard (seen here:
http://www.wgcshop.com/pcart/shopper...6CLHG_srch_G36)
Things you should consider though:
The G36 magasines cost a bit more than armalite types and they are also larger. Quite larger.