As per this Reddit post, Orisa's Fortify resists the following effects:
- McCree's Flashbang
- Pharah's Concussive Blast
- Junkrat's Concussion Mine
- Junkrat's Steel Trap
- Mei's Endothermic Blaster
- Mei's Blizzard
- D.Va's Boost
- Orisa's Halt!
- Reinhardt's Charge
- Reinhardt's Earthshatter
- Roadhog's Hook
- Ana's Sleep Dart
- Lucio's Soundwave
After additional testing, Fortify also resists the following effects:
- Soldier: 76's Helix Rockets (they have a very small knockback effect)
- Roadhog's Whole Hog
- Winston's Primal Rage
- Zarya's Particle Cannon alternate fire
- Zarya's Graviton Surge
- Symmetra's Sentry Turrets
- Bastion's Configuration: Tank