My last Airsoft skirmish was years ago. After about 6 hours of fighting in an unused factory a friend had access to, my NiMh battery died and wouldn't recharge before we were done for the day. Someone handed me a cheap springer pistol. (you had to manually cock it by retracting the slide for each shot) and it was decided I would be doing "special projects". Namely sneaking around and messing with the other team. So I just did things like play "camper" and shot people in the back. Acted like I was on the other team etc.
One skirmish, I just laid under a brightly lit window, in an otherwise unlit room, right out in the open, and just shot people with impunity with the cheap spring pistol.
Getting bored with this, I took a plastic Solo cup (red too, I believe) and filled it up with Airsoft bb's and ran up out into fire at the enemy line behind a wall of stacked lumber and screamed "
GRENADE!". And I threw the cup over the fortification at them. The bb's went everywhere and pelted them all nicely.
Totally killed the firefight as we had "Rambo" rules like in paintball, where if you touched an enemy with your hand it was a "knife kill" and they were out, but nobody had ever figured out a grenade before, and this was still pretty early in Airsoft's popularity where such accessories hadn't hit the market yet. And nobody knew if it actually counted or not.