I buy all sorts of stuff there on sale. Less and less fabric these days though, seems like their prices are just climbing too high on their good fabrics. If I'm going to pay LQS prices, I'm going to go to an actual quilt shop! The Joann's near me just jumped up their Kona to 8.99 a yard. That is higher than the LQS's charge!
I like rummaging around in their remnant bin, notions are often a good deal (on sale or with a coupon). Recently they had their quilting stencils on sale and I bought a few of those. Interfacing/stabilizer/fusible web is a good deal (on sale or with a coupon, again). Batting sometimes. Pillow forms (their deluxe one is pretty nice and holds up well). Outdoor fabric for certain projects... Vinyl, for various things. Or if you just need some really cheap fabric for a test or mock-up, they have loads of that. When they have the half-off red tag fabric I stock up on heavy fabrics for tote bags. Books, when on sale.
I do a lot of other crafting too, so I wander the aisles looking for deals on things like poly clay, beading supplies, papercrafting... I'm kind of a crafting junkie, I do a little of everything! Sometimes I find treasures in their clearance area too. They clearanced out a bunch of their purse hardware not too long ago, so I stocked up on D-rings, spring clips (like for keys), large metal grommets, and magnetic snaps.
After Christmas, I go when things are 70-90% off and stock up on gift bags, tissue, tags, etc. for next year.
Pretty much the only aisles I don't really go down are the wedding, food/cake decorating, and the faux flower aisles.