Normally you can only throw 1 grenade/molotov, or fire 1 shot of m79, but if you do the following trick you can fire 2 instead of 1. Quickly switch between 2 weapons, let's say you have grenade as main weapon, switch to dual ingram because it's fast and easy to switch, and switch back to grenade. Immediately after you do this, throw the grenade you'll find out that you are throwing 2 instead of 1. This can be done with all weapons but most obvious one are described at the beginning.