They make shoes just for weightlifting, but for WODs that include both weightlifting and running or other activities, you may just want a pair of flat shoes. Common examples include Sambas (by Adidas) and Chuck Taylors (Converse, most people prefer low-top) but really, anything that has a flat sole will do. You can also use these on strictly weightlifting days, making them more versatile than strict weightlifting shoes. That said, if you want a pair of weightlifting shoes, then go for it! But, you may still also want a pair of flat-soled sneakers for WODs that involve lifting and other activities.
I'm with Emily: on WODs that involve a run, I prefer to use my running shoes (I'm not yet proficient at the POSE method of running). On WODs that involve cleans, deadlifts and the like, I prefer to use flat-soled shoes. Weightlifting shoes are definitely on my list for next Christmas, though.