L4D411 community member PuffTheMagicDragon found an unlimited grenades glitch. It’s extremely simple to do – you need to find two grenades. Throw the grenade you’re holding, then within a second pick up another one. Your original one will appear where it was at first, ready to pick up. Repeat for unlimited grenades.
I took a video doing it in the spawn room, but any place where there’s grenades it will work (including finales).

