The airline-safe Gerber Shard incorporates six different tools into a single piece of metal the size of a key, and you can slide it onto your keychain for $5 today. It’s been slightly cheaper a few times in the past, but typically as an Amazon Add-On Item, meaning it would only ship as part of a larger order. Today though, it’s the ultimate Prime-eligible impulse buy.
I bought this last time it was on sale, and used it as my primary box tape cutter during a cross-country move. It was really impressive!