Pulse grenades are thrown EMP weapons. When they detonate, they emit a powerful electromagnetic burst which is only mildly harmful to organics, but can cripple anything with an electronic circuit. Thus, these high-tech grenades are your "silver bullet" against robots, but worthless against anything else. If at all possible, angle your throw to use a wall as a backstop in case of bouncing - the blast is large, but it's worth putting it where you can't miss.
Even though pulse grenades are near-useless against critters, take caution in using them. The player, unlike other critters, has no inherent EMP resistance, and will take full damage from pulse grenades if not wearing any armor.