Here's a few I use that I didn't see mentioned.

F8=object mode
F9=vertices
F10=edges
F11=faces

Hold down j when rotating to rotate in increments of 15 degrees.

Select 1 or more objects you want to isolate and then press Shift i, then to bring everything back, deselect everything and press Shift i again.

Select an object and press f to frame in on it. Or press Shift f to frame in on it in all view ports at the same time.

Cntrl d=delete history

Edit: oops, I meant Alt d= delete history..I use ctrl d for duplicating.