I've always loved the idea of grab bags. Sure, it can be a gamble since you pay and THEN you get to see what is inside.
However, I don't think you can lose with a grab bag from McMaster & Storm.
They are do a little bit of spring cleaning right now, so they are offering these $7 grab bags. Each will have a value of $30 inside! Once you look around their store, you'll quickly see that no matter what you get, it will be good!
Oh, and don't miss their cute blog!