I'm finding all the PUBG Mobile/Game for Peace collabs much funnier and interesting than Fortnite collabs (even though I wouldn't play either) solely for the grittier and realistic artstyle juxtaposition sticking out like a sore thumb.
Another special category for licensed gacha games that stayed alive in Japan but died in their global release instantly
Star Ocean: Anamnesis (14 Months Global)
Magia Record (14 Months Global)
Mass for the Dead (11 Months Global)
Symphogear XD Unlimited (77 DAYS)
Some weird scrimblos:
Puzzle Fighter (8 Months)
SEGA Heroes (15 Months)
Puchiguru Love Live! (13 Months)
Glee Forever! (US property, but reskin of the Love Live! game developed by KLab, the same developers. 10 Months)