You should always be careful with ultimatums, particularly when you're really just on a power trip and bluffing… Sooner or later, someone is going to call you on your bluff, and you're going to be left standing there with your hands tied, looking pretty silly. Still, this is a favorite tactic amongst toxic managers, who relish the idea of threatening their workers with firing more than J. Jonah Jameson. There's nothing they enjoy more than putting a proverbial gun to your head, putting your fam…