The mind boggles

Can you pull your pocket knife out while your riding your horse (or your iron horse)?. You might need to, but it's there in your pocket under your chaps where you can't get to it. But instead of under your chaps, your new belt buckle knife is right there on top, holding your chaps up. Out in a second to get you out of trouble.

Belt Buckle Knives | World's Fastest Knife

Another quote from the site:

You have to get it out. In some situations, speed is critical. In some situations, one handed operation is critical. In all situations speed and one handed operation is very convenient.

MCN says: They certainly is.