"Most people agree that virtual currencies are here to stay," the Winklevoss twins told CNBC recently.
Virtual currencies enable people to make payments in virtual online environments, such as when playing a game or on a social networking site. They are an emerging tradeable commodity and bitcoin—first created in 2008—has so far been synonymous with this movement.
Bitcoin is used to exchange online credits for goods and services and there is no central bank that issues them. Bitcoins can be created online by using a computer to complete difficult tasks, a process known as mining.
(Read more: Winklevosses: Bitcoin worth at least 100 times more)
The virtual currency has garnered widespread interest from policymakers, regulators and the media this year. Reaching fever pitch in April, its price fluctuated wildly above the $200 mark. On Tuesday it hit a new all-time high of over $900, according to major exchange Mt. Gox.
Bitcoin may be the runaway winner at the moment, according to Cameron and Tyler Winklevoss—who famously battled Mark Zuckerberg over the origins of Facebook—but they believe it is "very possible" that there could be more than one.
What are the alternatives to bitcoin?
(Read more: Bitcoin is tulip mania 2.0—not gold 2.0: Schiff)
CNBC highlights some the greatest hits in cryptocurrency, including defunct and dubious alternatives. These options are not for the fainthearted and are in are no way endorsed by CNBC.
By CNBC's Matt Clinch
Posted 19 Nov. 2013