All meat, but especially chicken, turkey, and pork. They are a hassle to cook right, leave gross juices everywhere, are cruel to factory farm, and super expensive. I rarely bother now, it's so much easier to get a consistent cook with tofu. Plus tofu is so mild that I can add whatever flavors I want.
This Thanksgiving I made a real turkey and a seitan turkey, and far preferred the seitan one. It tasted more like stuffing, and the turkey was tough despite being the exact right temperature with an instant meat thermometer.