Speedball or Sup'Airball. Fits my play style, quick, field-of-fire based, team work needed. Airball is ton of fun when you have a good team. I was on an amateur team for a while and I loved it.
As for realism, which has been discussed above. Go play airsoft, you can get some super tacti-cool stuff to play with.
But if you're going to spend that kind of money, buy real firearms. Once I hit the age of 18 I stopped buying paintball stuff and started acquiring bolt-action rifles and shotguns. Then at age 21 I started buying handguns and assault rifles.
I must say, I have ALOT more fun with my AK-47 at the rifle range than I ever had while playing paintball. Occasionally I'll get to go out and do some Run and Guns, which are sorta like shooting competitions, you run through a course shooting targets and stuff with your rifle and switch to your sidearm and engage closer targets.
When I usually do this, it's with my friends on one of our plots of land. It's kinda hard to get new people into it, the start up cost is a lot. Additionally, whenever we go out, we always have one guy be the safety officer for the day, or half-day. They have to watch everyone like hawks and yell at people who are doing things that could potentially cause accidents. When messing with real firearms, safety is the biggest concern.
Also, I'm selling a Smart Parts Impulse, with an O2 tank, Smart Parts FREAK Barrel and Halo B.