My brother gave me one of these hand cranked drills that he found in a thrift shop. It is quite old and made in West Germany. With wood drill bits it is the ultimate tool for drilling holes in thick leather or other belting materials. You get very clean and even holes that are unlikely to tear.

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That's the first time I hear of this application for drill ;D Do you clamp it between two pieces of wood or do you drill it just "freehand"?

I typically use one of these: https://en.wikipedia.org/wiki/Hole_punch#/media/File:Lochzange.jpeg

I clamp my leather securely to a table, use a piece of hardboard between the table and leather.
When the point of the wood drill bit has just passed through on the other side, I flip the leather around and drill from the other side.
I bought some cheap drill bits that I only use for leather. They stay very sharp and drill easily.  It barely takes any effort to drill holes.

those are neat.
But since I bought a decent cordless drill a couple of years ago - I'm amazed at how many things I use it for.
Particularly useful for reaming out holes in 3d prints when I print really fast (most of the time).

And with the cordless drill I can holkd the thing with my other hand at the same time.   

I use a device like the one Teg linked.  I've used a drill before but the leather got a little chewed up.  That may have been something with the bit I was using or the leather itself though.