Robin Hood was such a good archer, he split an arrow in two, nock to tip, at the very center of a bulls-eye. His famous feat isn't physically possible. Forget nailing fleas off a dog's back, that's like shooting through a skull, nailing a flea off a dog's back to another flea on a different dog, then pinning them both inside a rock... without harming either dog. And he did it with a longbow, a weapon designed to be fired at armies, not individuals (most competitive archers, including Katniss, use a compound bow). On top of that, Robin Locksley (known as Robin Hood), was a career soldier. He was both a master swordsman, and highly skilled with a quarterstaff. He often challenged random passers-by to duels, and always won, even against physically superior opponents (such as John Little, known as "Little John", who eventually became his best friend).
Robin Hood is also famously good at espionage, specifically infiltration and disguise. Basically, Robin Hood was the James Bond of the medieval age.
EDIT: Actually, no... this [http://www.fxnetworks.com/archer] is clearly the best Archer. HAHA! I SO CLEVAH!