If your goal is to be different than the other guys, and from the way you've worded this I'd guess it is the Bushmaster ACR will be your best bet.
G36 lots thanks to JG
HK416, good supply once again thanks to JG
M468, beyond rare, VFC kit was made that's out of prodcution
FN SCAR, fairly common
Bushmaster ACR rare now but coming available since A&K has just got the greenlight to sell them.
If I was starting up right now with a plan to be a serious player I'd be picking from the GBBR lineup instead of the AEG family.
Airsoft, where nothing is hurt but feelings.