If you're willing to do slightly more work, you can get a better deal. Chipotle will give you a burrito for $2 if you wear a costume into the store after 4 p.m. I have no idea what constitutes a costume, so somebody wear their workout gear into the store and say "I'm dressed as someone who is athletic" and see if you get a $2 burrito.
Freebirds is offering a monster burrito or monster nachos for the price of a regular burrito or nachos after 4 p.m. today. I don't think this is as good a deal, but you don't have to wear a costume or pretend to be wearing a costume.
Bike race at CG
Common Grounds and Bicycles Outback will be hosting a Ghouls and Gears Halloween Alley Cat Race. It costs $5 to participate and registration begins at 7:30 tonight with the race beginning at 8:30.
Bike night at QSL
If you want to pretend to be a biker (as in motorcylces) for Halloween, Quaker Steak & Lube is having it's usual Wednesday night Bike Night. Or if you're not into Halloween, but you are a biker then Quaker Steak & Lube is having its usual Bike Night.