Fandoms:

Final Fantasy X-2
Fire Emblem: Genealogy of the Holy War
Turning a Sphere Outside In
Monster Prom
Chihayafuru

Anything else: I love so much about IF - the way it can be a multi-sensory experience, the way it can explore What Ifs even within the inherently What If-y format of fanfiction, the immersiveness, the potential for surreality and uncertain reality...! Naturally, Monster Prom lends itself well to IF fic mimicking canon; maybe something like a Deep Conversation ala Road Trip, but more specifically tied to both the shipped characters. I also think it could be fun to explore multiple shipping through an IF; like, does Seliph end up with Julia or Ares or both or whatever else: your choice!! But even if an IF is super simple, my ADHD brain will definitely still enjoy the novelty! :P