9. Hammond Druthers
If Bryan Cranston makes a guest appearance in a sitcom, it's a practical guarantee that he'll steal the show. His HIMYM character, Hammond Druthers, is no exception. Druthers works as Ted Mosby's horrible boss then horrible employee for a few episodes in Season 2, then returns for a quick cameo in Season 9 to offer him a job in Chicago.
Druthers overtakes Walter White as Cranston's most evil character. Ted recounds a series of his cruel deeds in the Season 2 episode Aldrin Justice, such as denying his mother a birthday present, freaking out at a man for giving him a sandwich without horseradish, and knocking away the ice cream cone of a small child and laughing as he cried. (Though that last one may have been exaggerated.) Even so, Druthers turns his workplace into a hostile environment, and when Ted and Lily stand up to him, it knocks him down a peg.
Later, we see a down on his luck Druthers as Ted's friend outside of work, only to relentlessly antagonize him during office hours. Every time Ted tries to fire him, something comes up that prevents him, such as a notice that his wife is divorcing him or that his dog has died. Finally, Ted fires Hammond, only for him to suffer a very real heart attack, which Ted thinks is fake until the paramedics arrive.
Though Hammond only appears in three episodes, and one of those appearances is very brief, he makes himself memorable. Every audience member wants nothing more than to steal his Pete Rose Pete Rose Pete Rose baseball.