Here's the stuff I use.
PowerClean-Avalible at Autozone works good but, you have to scrub. Don't use on plastic.
Carb Cleaner- Easy and avaible anywhere. I usally buy the cheap stuff and keep plenty onhand.
Chemdip- Comes in a gallon can with a parts basket inside. Works well if you let parts sit in it for awhile. Horrible smell and will stink up everything including your house. The most effective stuff I've used for making bolts and stuff look new.
Lacquar thinner- Works on all kinds of things. Don't use it anything that has paint on it unless you want it to come off.
Acetone- I use this before welding parts and general cleaning for lots of things.
I've used MEK before and I think that is the craziest stuff I've ever used.