The compendium section on “Step 1. Make Plays” says that
Doesn’t this leave out deeds like Hart’s Tea Shoppe?
This is covered in the main rulebook p.21 under Make Plays
Shootout abilities you use must come from either an action card in your play hand (which is played and then discarded), a deed, an Improvement (a card with this keyword), your outfit, your legend, or a card in your posse (i.e. a dude or one of their attached cards). You can also use a Shootout ability on a card that’s not in a posse, but only if that ability would bring a card currently in play into a posse.