I do usually rotate my secretary from time to time and also check their walk/run animation if I get a new girl.

Longest staying :
Toad Lily (my 1st 5*)
Sasanqua (I kept staring at her eyes)
Mint (I just love her, go team mint!)


Unique run/walk animation :
Edelweiss (Go go segway!)
Hypericum (Trips on a banana frequently)
German Iris (Rocket Wand)

I also like german iris laugh, it's awkward and spooky at the same time like she is trying to laugh for the 1st time.