User:Will Thompson/List of words with two contradictory meanings

Incredible

 * 1) Too implausible to be credible; beyond belief; unbelievable.
 * 2) Marvelous; profoundly affecting; wonderful.

"Wikipedia is an incredible source of information!"

Forge

 * 1) to shape a metal by heating and hammering
 * 2) to make a counterfeit item of; copy or imitate unlawfully, e.g. money, a signature or document

"We have forged an alliance."

Arbitrary / Arbitrator

 * Arbitrary: Chosen for no reason, somewhat random.
 * Arbitrator: a person to which the authority to settle or judge a dispute is delegated.

(This one is tenuous, but they share a root an arbitrator's decision should not be arbitrary.)

Inspired by User:Benjamin Mako Hill/List of animals that are also verbs