This thread is a great idea!
There are several options to consider imo. If there is only space for one more currency, I really don't have an answer.
1 There are some currencies I find more useful or suited than others mostly because they have been around for a long time and have proved to survive for years.
2 Then, there are some who might create a lot of volume (not a fan of Doge though).
3 Also, there might be some innovative coins out there that may be worth supporting.
1 How about devcoin or namecoin or even ixcoin?
2 MoonCoin (love their space camp idea and even though the coin is only 2 months old it would create dozens if not hundreds of Bitcoins of volume)
3 DataCoin, (
) others that I know too litte of as of now, just too many fish out in the sea these days to check them all out.