I tend to have a goal for my shopping trip... It doesn't mean something else isn't thrown in with it, but I tend to stick to my original plans. Sale items tend to make me excited, and if I don't have enough in my cart to get free shipping, I'll add something else I like. (This applies to any online shopping site, mind you.)
I'm currently eagerly awaiting the Tantus General, which was the sole item in my last order. It's exciting and a little nerve-wracking, since it's going to be the overall biggest thing I've bought yet.