This is the time of year vacant strip mall store fronts suddenly become occupied by pop-up Halloween supply and costume outlets. I like to browse these for cheap stuff that may become useful for shoots at other times of the year. One of the things I saw a lot of this year are green screen body suits. Actually, they came in many solid colors, as well as black, white and tie dye. Under fifty bucks. Being able to manipulate objects on a set directly, using a guy in green, can be a useful post production trick.
Fog machine fluid goes on sale this time of year, and cheap, throw-away-priced foggers too, some come with remotes. When you, need that well-defined shaft of light thru a window, or a pool table or poker game scene, a boxing ring, spooky dungeon, fake house fire, battle scene, or a band video, nothing beats using a fogger or hazer.
Makeup is also cheap and plentiful. Blood packs, grease paints, more advanced prosthetic kits... cheap props... it's a good time to stock up and store away these treats against the day you suddenly need them for a legit production.