Silent Assassins Squad is a prolific (and well outfitted) milsim paintball team based out of North America. Their members maintain an active presence on various forums and social media pertaining to milsim paintball.
From what I've seen, these guys are truly dedicated to furthering milsim paintball and if you get the chance to play with them, jump at the opportunity. Or better yet, join up, as they are looking for new recruits in many regions.
SAS Youtube Channel
SAS Facebook Page