G36 - kinda bulky for me and carrying handle is, I think, useless. Still, many people love it
XM8 - if you'd take G36 and took away all the good stuff you'd get XM8. Never heard a good word about it.
M4/M16 - customizable! If you choose one of these and later decide to go for extreme CQB or sniper rifle, you don't have to buy anything new, just modify what you've got. I'm not M4 fan but this is good choice for everybody
Just goes to show, people with brain damage are the real heroes.