Most of the ammo that is in short supply in my WalMart is 22LR and the harder to find 22WMR. Other rounds like 9mm and 40 S&W are usually found. 38, 38+P and 357 Mag are scarcer and infrequent on the shelves. 45 ACP is a little better. You see Winchester Super X 45 LC sometimes, too.
Rifle calibers, 7.62X39, 223 and 5.65 are pretty well stocked along with many other calibers primarily used for hunting.
Look for Wolf and Tula to start getting sparse.
I have a hard time finding 44 mag for a reasonable price