seconding the reprints of the magnetic poetry and the stickers, those were super good and fun things.
an incredibly insufferable idea i had a while back for a doc that i think would make good merch was a book of fplus madlibs, like, taking some popular readings (the guy who's married to twilight sparkle, some of the passages from comixnix/self published authors, wizardforums) and just blanking the adjectives/nouns/verbs. could be fun!