Variant: Writing On the Blank Cards

House rules (the local rules, not the awesome podcast) and other player-created additions to board games have been around for ages. Ever pool the fines and fees in Monopoly and then give it to the person who lands on Free Parking? Yeah, that’s a house rule. That’s not how it’s “supposed” to be played.
Recognizing this tendency of gamers to adopt their own variants and changes, many game companies have started providing blank cards, blank tiles, and other items so that homemade concepts can be seamlessly integrated into the commercially-produced game.
So this week’s question is: What have you added to your blank cards and incorporated into your game?
Usually, I answer my own question first, but my experiences with blank cards have never worked out all that well. Since my group just comes up with an idea and throws it in there, it doesn’t really receive a whole lot of playtesting. As a result, the card is usually severely overpowered and breaks the game. We soon eliminate it and go back to the standard set.
However, since these items are included in tons of games nowadays, the rest of you out there must have some really good ideas for cards or components. What have you added to your game?
We don’t use the blank cards. One exception is Apples to Apples where we’ve added one. I think it’s Chocolate Covered Hookers. And there was one other that someone wrote that was in such horrible taste that I threw it away.