Oh boy. Most fun? Buckle in.
I ran a TTRPG using Pathfinder 1st edition, Mythic Rules, Campaign, etc. (the whole rule set). I set this in Skyrim, a few years after The Dragonborn put The Nords back in control.
I built a custom class for using Thu'um (dragon tongue), and each player slowly learned a handful of words over time.
Then, I made a system where they can shout in unison to create 'multi-word effects'.
The best two are as follows:
1.) T-Rex tornado. Sounds like what it's titled. The draconic words for "Teeth", "Claws", "Tempest", "Gale", and "Animal" resulted in an enormous tornado filled with T-Rexes flying across the battlefield.
2.) Insatiable Lustful Hunger. An enormous herd of scavenger beetles the size of mini-vans was descending upon a town. The party used the words "Passion", "Desire", "Flesh", "Consume", and "Spread" to cause basically a beetle-only zombie disease to spread through the hostile army's ranks.
Very fun campaign, even more weird stuff happened later on (a tank with a main gun that took 1 year to recharge but did 100d10 damage, and 1-shot a Kraken, for instance).
Lots of good memories.
