I use unibits, or stepped drills, constantly because there’s nothing better for drilling sheet material. Let’s say you need to make some holes in 1/16th-inch thick acrylic. Your standard two flute drill bit will just tear it to pieces. But the unibit does it without any chaff or shattering or anything. This is because it’s not fluted; it doesn’t pull itself into the cut. It makes the cut with its leading edge, and it’s effectively a scraper. The stepped shape — giving different sized holes in one bit — is simply an added bonus. I use them for all kinds of sheet materials, so I’ve got a ton of them.
[We first reviewed the Unibit back in 2008. Thanks, Adam, for the update!--OH]