Goddamned Bats/Tabletop Games

• In Warhammer, there are a number of units that will have the player using them laughing in glee as the opposing player growls in frustration. The Lizardmen have Skink skirmishers-- small and skittish blowpipe users with Poisoned Weapons that love hiding in terrain and can shoot in any direction.
• Pugwumpi/jackalrats in Pathfinder: tiny, very squishy humanoid fey with just enough damage reduction and spell resistance to be annoying at the low levels in which they're normally encountered, and no particular offensive prowess besides the mind-bogglingly annoying "bad luck" ability that, in game mechanics terms, forces players to roll their dice twice and use the lowest result. Since low-level parties are particularly dependent on the grace of the Random Number God to get anything done, this can make fights against the little wretches annoyingly drawn-out, despite the fact that a solid blow from even a low-level fighter could kill them.