I'm trying to remove the shower stem so that I can take it to a home improvement store and find a replacement. I have a shower stem socket that I am attempting to remove the bonnet nut with, but it won't budge at all, no matter how much leverage I try to apply to it! I'm not sure if maybe I am just not strong enough, or if there is a trick to it? The stem looks pretty worn to me, and maybe the parts have been in place so long that they are stuck there? Any tips on how I can remove this stubborn nut?

I am putting up a image of a shower valve. Notice that it isn't the bonnet packing nut that you must remove. It's the larger stem and washer restraining nut that you need to remove. Did you back the stem out a bit before you attempted to unscrew the retaining nut? Some WD-40 on the threads might help. Good luck, Tom

Kissler & Co., Inc. (http://www.kissler.com/)
If it is a kohler with square handles it is a kohler 'trend' faucet. It takes a 6 point 1/2" drive deep well socket to remove it. Remove the plastic parts so the socket will go over the stem.

I'm trying to remove the shower stem so that I can take it to a home improvement store and find a replacement. I have a shower stem socket that I am attempting to remove the bonnet nut with, but it won't budge at all, no matter how much leverage I try to apply to it! I'm not sure if maybe I am just not strong enough, or if there is a trick to it? The stem looks pretty worn to me, and maybe the parts have been in place so long that they are stuck there? Any tips on how I can remove this stubborn nut?
Get a plumber

For a do it yourselfer, this is not helpful...