The "iconics" almost never show up in my games, because they never feel right -- they always felt more like something rather silly or just something created to deal with the rules.
Mytholigical? Often, if they feel like they fit. Legendary? Sure, again, if they feel like they fit. Low-level creatures and humanoids who are classed? Constantly; they are the main villains, especially the undead (ghosts, vampires, zombies, ghouls, skeletons, etc.).