Some bands encourage fans to buy or bring specific merchandise in a special form of audience interaction. Generally, it involves waving something like a towel or light around during certain songs and becomes fan tradition after a while. If you're headed to a concert and want to be completely on top of things, you'll want to know if the band you intend to see has a tradition like this. Here is a partial list of bands, the items they use, and the songs they are used in. Please feel free to add to this list.

Band
Song
Item
alice nine.
Velvet
Pen light
Antic Cafe
Bonds ~Kizuna~
Band towel
Kaggra,
Unknown/multiple
Folding fan (doesn't have to be band merchandise)
Miyavi
Shouri no V-Rock
Miyavi towel