Coolest action feature?

[Lich Leech]

My fav as a kid was always the Battle Armor chest. I found that endlessly fascinating

[Collec-Tor]

The flippy-flippy Battle Armor!

[Neophron]

I'll go for Hordak's variations (ordinary, Hurricane, Buzz-saw).
To be honest, I guess Hurricane Hordak is better than other two for having 3 interchangeable propeller-like weapons.