Rapscallion: a mischievous person.
This is one of those words that conjures up a whole array of other, equally awesome words: rogue, knave, scoundrel, varlet, slumgullion.
This word seems to have first appeared in the late 17th century, and is closely associated with the word rascallion, which was an earlier elaboration of rascal. Dictionary.com gives it a specifically feminine parallel in the word rampallion, which is yet another awesome word and came from the Middle English word ramp, meaning a rude or boisterous girl or woman.
Now, I love a good, rude, boisterous woman, so I found this quite fascinating in itself. In Middle English the word ramp also referred to an animal climbing or standing on its hind legs (such as in rampant, used in heraldry to indicate a beast depicted rearing up). Ramp, as a perjorative term for a woman then later became romp in the 18th century, defined in Johnson’s Dictionary in 1755 as “a rude, awkward, boisterous,untaught girl.”