I like it without any nicknames. I don't know how many I've even met because most of them go by nicknames that are also common to other names like Kaitlin/Caitlin/Katelyn/Katrina/etc.
I used to like
Catherine best because it looks soft and classic. Then
Katherine grew on me and now that's my favorite spelling.
My favorite nickname I've seen is a
Katherine (actually it might have been
Katharine, which I don't like) called Katyana.