The difference between a classy criminal and a lowly thug is that while the latter personally whacks those who've wronged him, the former hires a professional, then attends his daughter's oboe recital. If someone's wronged you, stay classy, with TheSpiteSite.com.
Founded by a Chi couple, Spite specializes in sending anonymous "Nasty Grams" via snail mail to whoever pissed you off; the invitation-sized cards feature sketches in 50s Americana, Pop Art, and groovy 70s styles, and're sent in a fiery red envelope with postage hand-affixed to avoid tracing. The 30+ smackdowns (all $2.99) range from the slightly pissed (a Scrabble styled "Mind Your Own Business"), to the mean-spirited (a condom hanging from a clothesline declaring "You Were A Mistake"), to the unforgivable but likely true ("Your Cooter Stinks"). You can also send a snack with your spite: a takeout box containing fortune cookies stuffed with wisdom like "Karma is a Bitch" and "P.S. Go F**k Yourself" (adding insult to injury, it will not tell you how to say "Duck" in Chinese).
For spontaneously delivered justice, check out the "Vengeance" biz-card ten-packs, which include a businessman scolding "Nice Parking Job, A**hole!", and a waitress standing next to the note "Roses are red/Violets are blue/Your service sucks/No tip for you" -- hand it off, and if you're truly classy, you'll stick around to savor your pie.