I have a Tokyo Mauri FN-P90 "triple rail" like this one:
http://www.precisionairsoft.com/item918.htm
It's loads of fun, and much cheaper than paintball. I've got plenty of real firearms such as AR-15's, AK's and a FAL in my collection, but at the time I thought the FN P90 would never be for civilian sale. So choosing this was partly in response to that. (A semi-auto "real" P90 is coming out next year for about $1500 with a long-barrel that sticks uselessly off the front to make it US-civilian legal. Still expensive, and the ammo is too…)
I bought it from a friend who'd been a paintball buddy in the past, and turned me onto Airsoft. He runs a "Dungeons 'N Dragons" game store and carries paintball and Airsoft as well.
The ergonomics are great, it's one of the newer designs so the motor and gearbox had features older designs like the M-16 and MP5 copies at the time needed "upgrades" to get. The "real" P90 is not really the commando/SWAT weapon it's played up to be on TV. In reality it's original designed intent was to be a small, portable, and user-friendly defensive weapon for army's cooks, drivers, techs etc. who might get attacked, but 99% of the time don't need the full sized assault rifle. It's supposed to lay down lots of moderate powered, but pointy, lead keeping the enemy at bay until dedicated combat troops arrive to rescue them…
Since players are supposed to keep their Airsofts clocked at 300 fps or less, just like paintball, I also figured the smallest and most convenient package would also be good for play. The ballistics are also that of a round ball like any other BB, but in Airsoft they're given a downward backspin. Like a baseball pitcher throwing a curve ball, but upward instead of sideways, to fight the natural drop of gravity a bit longer. This flattens the trajectory somewhat and is called "Hop Up". Most good Airsofts have this feature. Since I have a red-dot scope on the sight rail of my Airsoft P90, there's also no advantage in a longer barrel like there would be with using iron sights.
Like it's real counterpart, the P90 has the non-traditional horizontal top-mounted magazine. I found it convenient for making magazine changes while prone under fire without having to lift up a bit like a normal rifle with the magazine on the bottom.
Before my kids were born, (two sets of twins in the past 18 months, so this is not that long ago…) we'd play in an old factory being used as a carpentry shop. One of my friends-friends worked there, and the owner was cool with letting us play in the unused areas on the weekends. Lots of fun, and not having to deal with paintballs or gas, made for more play, and less "get ready" time. As you'd imagine eye/face protection is a MUST. Otherwise, Airsoft BB's hurt less than paintballs, they have a similar velocity, but weigh much less. They will leave small welts on exposed skin. The one major drawback over paintball is that play is on the "honor system" so you'd better be able to trust the other players.
If you play indoors on a hard floor, I recommend hard knee pads (they're handy outdoors too) but you don't know the meaning of pain until you kneel down on your kneecap with a loose Airsoft BB between all your body weight and a concrete floor...
One excelent feature that you can add to Airsoft that might interest the Flashaholic:
You can buy after-market "silencers". In reality they're a Xenon flashcoil surrounding the flight path of the BB, tripped by an internal infra red beam. And you can buy GITD (Glow in the dark) Airsoft BB's which looks wicked-cool in a dark room or at night.
If you've watched "Lost in Translation" that Bill Murray movie set in Japan that won all those awards last year, there's the one scene where he and Scarlett Johansen are kicked out from a kareoke bar when their Japanese friends get rowdy. The barkeep drives them from the bar with an Airsoft with this feature. When that scene played my wife went all wide-eyed and, WTH?-like. (I could see the mental gears turning, "They have RAY-GUNS in Japan?") I quickly explained and we went on with the moive.