Just got a formula with locking lug nuts. Guess what. The key is gone. Not one in the car anywhere. How many types are there? Best way to get them off. Still 3 on the car. One was removed by previous owner.

Yep, search on youtube. Entertaining, at least.

Leave the car overnight in the wrong side of town and some helpful people will take care of it for you.

If they're factory locks, there are at least 15 keys. You can try sweet talking the service manager or parts counter monkey at your local GM dealers and see if they have the master set of keys they might be willing to let you take to the parking lot and crack loose your lugs. But inevitably, they'll be missing 3 keys (including the one you need), and there will be 10 or more duplicates so after 45 minutes of trying different keys you'll end up pounding the largest socket that won't slide right over the lug, onto the key and cracking it loose with a breaker bar.

I couldnt find my lug key and ended up just hammering a cheap socket on them and they came right off, a month later I found the lug key

Easiest thing would be pounding a socket over it then using a breaker bar. Like Drew said, GM used alot of locks so the chance is pretty slim of finding the correct one.

12 pt socket. Find one that is just a little smaller than the nut. Pound it on with a hammer. If I remember right a 21 mm should work

Got the kit from O'Riley's and was able to get 2 off before it got stuck on the second one. Found a key from another car that was close enough to pound it on and get it off. The kit cost close to 20.00. morale of the story. Be ready to buy replacement sockets