I thought the One Away million dollar bonus was the quintessential example of what it should be, because it didn't feel ridiculous and tacked on. So on that note, you could easily do "first try perfection = $1,000,000" for games like Switcheroo, Race Game and Bonkers. Switcheroo would probably be best, because you could build properly to the moment, whereas Race Game might be a disaster where the contestant uses a ton of time for their first try, blows it, and just has time for one more set of changes.
-Jason