As a promotional contest designed to push Bing Shopping, Bing has launched a one-day sweepstakes that will give $100 Amazon gift cards to five lucky participants. And it’s all taking place on Twitter.

The contest involves tweeting your all-time best costume to Bing, and if Bing selects your idea and retweets it, you win the money.

With Halloween right around the corner, people are racking their brains to come up with creative costume ideas.

Well, we want to help those folks find some inspiration so we’re inviting you to share your best Halloween costumes with @Bing. Simply tell us your all-time best costume and we will give five lucky respondents a $100 Amazon gift card for sharing.

In order to enter, you must follow @Bing on Twitter. Then, you tweet your all-time best costume @Bing with the hashtag #BingHalloween. If yours is picked, you win.

The contest is running today, October 25th, from 10 am to 8 pm EST. The five winners will be selected throughout the day. Each Twitter handle only gets one entry.

What was the best Halloween costume you ever designed? Tell Bing and tell us in the comments.