For this activity, I gathered a bunch of flyers from holiday sales and such. Then I gave the students the challenge of spending $500 on items they found in the flyers. I even gave them some coupons to use on specific types of items, i.e., 15% off any shoe or sock. They have a paper to fill out with the price, coupon/discount, and final price of the items they choose. If you have time, students can cut out the items they are purchasing and paste them to a poster with the coupons or information about the sale.
I think this activity is unstructured enough that you could challenge students to get the best deals or buy the most items or see how tax affects the final costs of things. You can also use catalogs instead of sale flyers if you prefer students use the coupons on items that aren't on sale. You can find a website with Black Friday flyers to use if you'd rather not have all the paper -- it can get messy!