Updated with additional comments regarding Android.
Consider it an early holiday present from Halfbrick Studios, as all of the developer's games on the iOS App Store will be free until 10PM PT tonight. That includes such classics as Fruit Ninja, Age of Zombies, and Monster Dash.
Halfbrick CMO Phil Larsen announced the deal on Twitter, and told Polygon it was a way for the company to give back to its community. "Now it's time to give something back, kick some ass and start 2013 with more momentum than ever. Have a blast playing Halfbrick's finest," he said.
If you are looking for some free time wasters for your iPhone or iPad, then grab them quick. The sale doesn't cover Android versions of the game, as Halfbrick's Phil Larsen notes that these games are "already available for free with ad support" on Google's mobile platform. He also notes that "the Android version is currently out of date, and our dev team is currently working on it to update and ensure the latest version is live around the world. We don't want Android users excited about a promo for an outdated version, we want them to have the best."