Constructor/YMMV


 * Game Breaker: Mr Fixit's plumbing sabotage. It can level an entire block, takes three repairmen to counter, and the AI doesn't know how to deal with it.
 * Goddamned Bats: Enemy Foremen attempting lot takeovers. Unlike undesirables, they can use subways and police ignore them. You have to manually direct a unit to chase them away, then dedicate money and workmen to repairing the damage they do. Worst of all, some fences will bug out and never get repaired, forcing you to demolish the block and rebuild.
 * Ghosts. They're immune to police and guard dogs, can't be attacked, and once they've haunted one of your houses, only a Ghost of your own can reliably remove them.