We've featured Threadless t-shirts quite a few times on ComicsAlliance thanks to the frequent geek and comics-friendly shirts and designs on the site involving superheroes, supervillains, queenly Jokers, literal batmen, out-of-work crimefighters, batsignals, useless superpowers, and sexy Transformers -- not to mention designs from comics creators like Jess Fink. Today marks the 10th anniversary of the online store, which is currently having a $10 sale on all shirts till 10 AM on Saturday. To celebrate, we're going to giving away two $50 gift certificates to ComicsAlliance readers.

Just drop a comment on this post telling us which Threadless shirt (comics or non-comics) is your favorite by 6 p.m. EST on March 23rd and you'll be automatically entered. Remember to use your correct e-mail address when you comment, and read the Official Rules and check out the fine print after the jump for more info.

ComicsAlliance's Threadless giveaway is open only to legal residents of the 50 United States, the District of Columbia and Canada (excluding Quebec) who are 18 and older. To enter, please use the form on this post. You must enter before 6 p.m. Eastern Time on Monday, March 23, 2010. You may enter once per email address, and ten winners will be selected in a random drawing. The prize pack will include the following items: 1 gift code to be redeemed on Threadless.com (approximate total retail value $50). Click here for complete Official Rules.