Any domain name with the word "jon" in it is pretty cool. The letter "J" is not very common, and simple multiplication show that combinations of particular pre-determined letters are even rarer still.

It would proably be hard to get a personalized license plate with "jon" on it, ergo, it would be a cool domain name.

Jon:

I would say that made up words like "google" and "flikr" and "ebay" are cool, in the domain world.

There are some good websites that help you find these kinds of domain names. An example is: DomainPigeon.com.

DomainGroovy.com has a nice list of tools for finding the perfect domain name.