I like expensive heavy steel roasters and nice ceramic gratin dishes as much as anyone, but I've come to realize my most versatile and most used piece of ovenware is my good old Pyrex 9X13 pan. Dollar for dollar it's about the best thing in my kitchen. I don't have to worry if it gets a couple scratches or some baked-on oil around the rim, I'm not going to baby it. If I take it to a potluck and it gets broken or lost, who cares? They're cheap, I'll get another one. I also like how the width fits a standard roll of foil or plastic wrap.
It's great for lasagna, enchiladas, gratins, any kind of roast vegetables, chicken, ribs, and all kinds of baked goods. I can brine a brisket or cure a salmon in one. What else am I missing?