VFC SCAR Light, you will not regret it! Got mine last year and have probably fired 50000 bbs through it, haven't had a single issue.
I installed a tightbore barrel (although you really don't need to), and it's definitely the most accurate gun out of the guys i usually play with.
Folding stock is awesome for those tight areas, i've folded and unfolded it hundreds of times and still works flawlessly (i thought the hinge plate issue mentioned earlier was resolved in 3rd gen models).
If you're looking for an M4, go with King Arms (probably the most recommended gun on this site, affordable and still high quality). That was the first gun i purchased, followed by the VFC Scar Light.