i have a stainless steel kbar knife that has seen better days. what can i use to remove rust and polish the blade?

WD-40?

I'm not sure about stainless, but I resurected and old carbon steel knife with Naval Jelly,sanpaper stell wool and elbow grease. Then I sharpened it all up with the Lanskey sharpening system. It still looks pitted and ugly but you can shave with it!

steel wool ?

Yeah I used it early on to really work in the naval jelly on the body of the blade. This knife was absolutely trashed and I was going to throw it away, now it's my favorite knife! I've had it since I was six, and I'm fifty now!

If you have a gunsmith in your area, see if you can get him/her to run the blade across a buffer. It will get rid of all the rust and oxidation very quickly. Just make sure to run the blade facing down when doing this.

I thought stainless steel wasnt supposed to rust?

You could try some Rust & Blue remover. I think Birchwood Casey sells it.

Cheap stainless does!

Sandblaster?? Then oil & emory cloth??