A guerdon is a reward. The disappointing guerdon for your day spent shoveling your elderly neighbor's driveway might be a little tin of very old licorice candy.
The word guerdon, pronounced "GER-dun," is an Old French word that literally means "reward or payment." Though it is rarely used today, there's no reason you can't use it to describe the compensation you get for some achievement, like the guerdon you received when your essay won the writing contest — guerdon is another term for "prize money" in this case.