The wall oven. I think whoever invented this in its' dual format should be sainted. How can you do a large dinner or holiday gathering without one and keep your sanity in tact. To me, it does not matter how many photo's appliance manufacturers take of an oven with three or four racks, loaded with food and all looking gloriously browned and done - this has never happened in my life. Overcrowding does not make for even baking, even with convection.
This is why I think the Dacor Epicure Discovery Dual Wall Ovens are a must have if you are a serious cook or baker. When I need to do a batch of my famous giant cut-out cookies, it would take me eight hours to do in one oven what can be done in two here.
These ovens also have a probe so you can insert into both ovens your main course, i.e. turkey, ham, beef tenderloin - set the oven for the desired temperature and walk away. Now this is worth celebrating. You can actually cook AND enjoy time with your guests. Full-extension glide racks allow you to pull out your food and not have to reach your head inside to get leverage. It even has a Sabbath setting to conserve energy. A true investment in your kitchen's future!