Windows Explorer? It's not that bad. Granted, I only ever use it with the keyboard. But then you can tile two windows side-by-side (or four) and it's a bit like a commander of sorts.

The only time I ever have to use the mouse in WE is when I try to move to the Quick Access side-bar: sometimes focus gets lost somewhere around all the bloody menus I never use and I can't place it where I want it. It's weird and I'm not describing it clearly because it happens only occasionally and I don't understand exactly how.