Easy to produce, can use it for heating, driving, farming, etc. And you can put the various ways of using diesel together into interesting combinations:
http://cgi.ebay.com/ebaymotors/aw-cgi/eBayISAPI.dll?ViewItem&item=1806375724
This one amuses me because I have a 2-cyl Yanmar diesel tractor for small utility work that happens to be a 17-HP like this Kubota engine. I like the glow plug operation too.
Here's a pic to view after the auction is over: