War Thunder

Vehicle combat across ground, air and naval, spanning the 1930s to modern day. It is free to play, which makes it the easiest game on this list to get a group into - nobody has to buy anything first.

Squadron battles and co-op are where a community actually matters. A coordinated squad of three covering each other's flanks plays a completely different game from three solo queuers in the same match.

Progression is long and the grind is real. Playing with people who already know a tech tree saves you a lot of wasted research, which is another good reason to ask in voice before committing to a nation.