Even though I have accumulated a lot of cool mounts, I still find myself using mainly one mount: The Headless Horseman Mount. It was the mount I won last year during the Halloween Event.
One main reason I use only this mount is that because it functions as ground mount as well as a flying mount. So I only need one keybinding slot to mount anywhere, freeing up much precious spellbar space for macros like “/spit”.
Another big reason I use this mount all the time, is because you can use this mount while riding in vehicles!
If you jump into a passenger seat of any vehicle (or even driver seat), you can then mount on the Headless Horseman Mount, and it will still work. This draws a lot of attention anywhere you go since everyone will just see a horse riding around on a motorcycle.
Bonus for any motorcycle owners: If you use the [Iron Boot Flask] while driving around on your motorcycle with a passenger in the seat, you will still transform into an Iron Dwarf, but for some reason, it will also flip the passenger cart upside down, and it looks like your dragging the passenger around, face down in the dirt.
Speaking of the Iron Dwarf flask, this is one of the few mounts that you can actually use the flask to transform into the Iron Dwarf form without dismounting. Here are a few more examples of using the Headless Horseman Mount with other vehicles: