Fun class choices for a mount?

[Isamu Dyson]

Has anyone here ever given their mount class levels? If so, which choice(s) ended up being the most fun?

[Elric VIII]

I once had a character with a skeletal warhorse that was awakened, took levels in Warlock, and used Eldritch Claws. That was amusing.

[Jeff the Green]

Totemist could be fun. I'm imagining a horse with fangs, claws, and a petrifying glare.

It also saves you from having to buy magic items for it.

[Psyren]

Psion. Because {gently caress} you, that's why.