We like their fake Triscuits.
We try not to buy much there, but one must-have is their half gallon jars of olives. Best deal we've found on olives. Of course if you don't go through olives very fast, that might not work for you.
Otherwise, any kind of consumables you might use, like toilet paper, paper towels, dishwasher detergent, cleaning supplies, shampoo, etc.
We won't touch electronics there. We've had too many incidents where we've gotten home and found out the packages had been opened and the item wasn't all there or didn't work. Due to the frequency of this happening from different stores in different states and including their mail order stuff (remember the lap stand fiasco of 2012?) we've concluded it's their policy to put returned items back on the store shelves without verifying whether they work or are damaged or not. NOT cool!
Meat and produce are terrible at every WM we've ever been in. Milk can be a good buy, but compare prices.
Cat litter is sometimes a good buy, but compare prices.
We mostly shop at WM when we're on vacation because WMs are easy to find and have trailer-friendly parking lots. Otherwise, we avoid them too.