1)
Dogecoin (most surprising and ameable coin)
2)
Namecoin (the first altcoin ever, bitdomains are finally getting some traction)
3)
Devcoin (still a very unique and old (in bitcoin - years) altcoin, has active community of writers and devs, incredibly cheap at the moment)
4)
Quarkcoin (good community, interesting supporters in media, is in-game money)
5)
Darkcoin (very outstanding features, proof of service, masternodes, has
"Veni, Vidi, Vici" potential!
)
If I could add more, I would say Goldcoin, and Zetacoin.
Also: my list is not listed in order of priority, I find all those coins
equally promising.