Whose fans are the most dedicated? Is it Katy Perry's Katycats? Rihanna's Navy, Gaga's Little Monsters, Taylor's Swifties or One Direction's Directioners?

Well, we'll find out when some of the year's biggest fan armies battle it out to earn the crown for Best Fans of the Year in MTV's "Last Fans Standing" competition. Kicking off Wednesday (December 5) with 16 dedicated fanbases in the running, followers should head over to MTV's Facebook and rally fellow fans to "share" your favorite celeb's photo as many times as your fingers will allow.

The seven acts with the most post points will advance to the next round, set to go down during "The Big & Best of 2012: A Year End Celebration Presented by T-Mobile" live stream on Wednesday, December 12 at 12p.m. ET. During that unprecedented, eight-hour event, the remaining armies will compete in a series of online and interactive challenges, before we name 2012's Best Fans of the Year.

The fan armies in contention are: Katycats (Katy Perry), Rihanna Navy (Rihanna), Little Monsters (Lady Gaga), TWFanmily (The Wanted), Swifties (Taylor Swift), Selenators (Selena Gomez), Animals (Ke$ha), Directioners (One Direction), Beliebers (Justin Bieber), Barbz (Nicki Minaj), Glamberts (Adam Lambert), Hooligans (Bruno Mars), Lovatics (Demi Lovato), Team Breezy (Chris Brown), Beyhive (Beyoncé) and Team Britney (Britney Spears). Only one army will emerge victorious.

In addition to bestowing the title of Best Fans of the Year, we'll also present four other year-end lists as part of Best of 2012 Week. Beginning on Monday, December 10 and running through Friday, December 14, we'll reveal who came out on top in categories including Song of the Year, Artist of the Year, Movie of the Year and Clubland Pick of the Year. (Stick with MTV News all week for more details.)

The live stream on 12.12.12 will kick off at noon and play out across digital properties, including MTV.com, VH1.com, CMT.com and ComedyCentral.com, highlighting the music, personalities and pop culture moments that defined the past year. The blowout party will include eight hours of programming and highlights from MTV, VH1, Comedy Central, CMT and MTV2.

But wait, there's more! Carly Rae Jepsen will reveal her top five moments of 2012. She'll be joined by performers Grace Potter, Canadian indie rockers Metric, English buzz act alt-J, country duo Thompson Square, folk duo First Aid Kit and country singer songwriter Dustin Lynch, who will perform a surprise duet. Your hosts for the event are MTV News' Sway Calloway, VH1's Carrie Keagan and CMT's Kourtney Hansen, who'll broadcast live from MTV's legendary Times Square studio and on location in music venues in New York City, Boston and Nashville. (Additional performers and celebrity guests will be announced at a later date.)

"Big & Best of 2012: A Year End Celebration Presented by T-Mobile" goes LIVE at 12 p.m. ET on 12/12/12. Watch at bigandbestof2012.com for eight hours of live performances, surprise guest appearances, prize giveaways and special editions of "Rapfix Live," "Big Morning Buzz Live," "You Oughta Know" and much more!