Of course bitcoin. Any doubt about it ?
In case you missed it, this is the "
Alternate cryptocurrencies >
Altcoin Discussion" section, but thank you so much for bringing Bitcoin to the attention of this thread. Glad you're here to give Bitcoin it's due.
Back to reality:
UltraCoin ... Easy money
But the question didn't specify Altcoins, and Bitcoin and most altcoins are pretty much joined at the hip, so I'm saying Bitcoin too.