Grenades

Long carried by infantry soldiers to aid in removal of pesky hardened positions and enemies hiding behind things, grenades are quite simple in theory. When used properly, grenades do a bang-up job of taking out cars (and anybody who might use them for cover) and clearing out closed in areas filled with opponents. When used improperly on the other hand, you can just as easily blow yourself up and/or any cars nearby you may be using for cover. If you're not careful, you might also end up causing a chain reaction in congested areas which ends with exploded cars all about and lots of police attention. But then, that may very well be the desired effect in some cases. In GTA IV, Niko can drop a live grenade to the ground, but must run for cover before the grenade detonates. Niko can also cook a grenade and then throw at enemies for a short time. If Niko cooks the grenade too long and not throw at enemies, the grenade explodes, killing Niko.