rite that gatorgrip thing is wank! i tried one on my mrs car the other week.. and guess what i broke the fucker! did use a BIG breaker bar though and all my weight (i had previously gunned the nuts on )
It depends on the type of nut really! the ones on my cab you could just get a 17mm socket and bash it on.. they come off no problem!
On my mrs car.. they its PROPPER hard as they are just round! the only thing the locking key fits into is 4 little dimples in the face of the 'nut'
I ended up having to get a 6 sided, 12mm, deep, 1/2" drive, impact socket for my ex-girlfriends dad who sells snap-on stuff to get the buggers off!