I think
Bo is really cute! It's a proper full name here, but I think it's so short it works better as a nickname for something. That's how I suddenly thought of little
Bonifatius "Bo" in The Thief Lord and realised what an awesome name
Bonifatius is. :)
I like
Beau, but not as much as
Bo. It took a while before I realised how it's pronounced, I thought is was byoo like in beautiful for a long time.