most awesome money?

Just got home from a trip back home....wait. Let's try that again. Just got back to London from a brief visit to Virginia. When I finally got all of my crap unpacked I discovered four different currencies in my travel purse. Pounds, Canadian whatevers, Euros and American Dollars. What am I going to do with 10 Canadian whatchamajiggers? I mean, it's pretty and all, but useless unless I happen to layover in Ottawa again. 

This begs another very serious question for the world traveler. Which money is the best? I'm taking votes here. The results will be judged on your best argument for categories other than exchange rate: 

1. cool-looking 

2. usefulness (coins vs. notes, denomination efficiency) 

3. transferability (where it can be used.) 

Here's your big chance to rant about how boring your money is or how totally awesome. 

Go.