Part of my job working for a property manager is to clean vacated apartments. As you might imagine, some of them are pretty dirty. By far the best cleaner I have ever used is Castrol Super Clean (I think it's an engine degreaser). One gallon will make about 25 gallons of household cleaner, when diluted with water. It will clean ovens when used full strength (make sure you have lots of ventilation). but do not apply full strength to painted surfaces (it's also a pretty good paint stripper!). It costs about $6 at Walmart or auto part supply places. I use it to clean everything except glass surfaces, and it would work for that too if you don't mind rinsing. You can even use it as a laundry prespotter when diluted. About a year's worth of household cleaner for $6 seems to me to be a thrifty tip!
(I guess any engine degreaser would work the same, but I have experience using the Castrol Super Clean)
Well I work in the power equipment business and can verify that super clean used full strength is the best degreaser on the market by far. It's not the same as other degreasers though in that it's not petroleum based.
Super clean is also very caustic at full strength. Use extreme caution when applying it with a spray bottle. You may not even notice some of the mist got on you until it starts to burn your skin.