
Children, such as those found in Freeside, can not be harmed or killed, at all, ever. If all other paths fail, 'Wild Card' is the fallback. Yes Man is the 'only character that cannot be killed' that the devs bragged about, because he is required to trigger the final quest. This is explained in that he is not actually a specific Securitron, but rather a program (more like a virus really), that can run on any Securitron, and if the one which he currently inhabits is destroyed, he will just download into a new body. Yes Man technically can not be killed. He is 'killable', but he is unreachable, rendering that fact moot. The Gun Runners Vendor-Tron outside Freeside cannot be killed because he is behind a wall that cannot be passed without using the console to no-clip through. That said, there are, technically, 3 exceptions. The final body count reportedly clocked in somewhere around 2500-3000 kills. In fact, it was reported before release that one of the pre-release playtests consisted of a run through in which noone was spared. You can kill every NPC in the game according to the developers, save one. Contains a small amount of high explosives, the container itself forming most of the damaging fragments.
Certain grenade models are more effective against some targets, and less effective against others.
Most contain an explosive payload designed to inflict damage in a wide blast radius. Unlike Fallout 3, no NPC's have 'plot armor' or are otherwise permanently flagged as 'Essential'. A grenade is a thrown weapon that appears in all of the Fallout games.