for the one who is in undertale au fandom
i usually use this characters :
classic , fell , swap(some time blue) , ink , error ,dream , nightmare, epic , cross , lust , horror , dust , killer , outer , geno , reaper ,swapfell (blackberry) ,fellswap(raspberr) , dreamswap character , fresh (not so much) 
swap and blueberry are different , swap is the cannon underswap sans and blueberry is fannon version of underswap sans 
anyways , my favorite sans is outertale sans , then you would see him a lot in my stories 
i add storyshift to , he is one of my favs to anyways that all
i don't do oc and reader book
i know some other character that i might add , gaster gang , naj , empireverse , bad time trio , good time trio and staller time trio , 
if i do ships i do such ships :
dustberry
afterdeath
bloodylove 
outerkiller 
kustard
cream
epiccolor
inkerror
for nightmare fans i might do one of this :
fluffynight , swadmare , if i don't ship killer with anyone  killermare (low chance) , errormare