It's only slippery if you don't have proper footing when punching a Nazi.

If you can't ensure proper footing, or are unable to properly punch, a baseball bat will suffice. Preferably a wooden baseball bat, as aluminum bats flex more than wood, and you don't want any give when hitting a Nazi with your bat.

Aim for the knees, so the cowardly Nazi can't run away, like the coward it is. Once it's on the ground, you can continue to work the rest of the body. Stay away from the head! I cannot emphasize that enough. You want the Nazi to remain conscious, so it can feel it's bones shatter.