We had this thread in ye olde forum didn't we? Well, here it is again. All you need to know is in the title really. Get inspiration from the user's avatar, signature, gallery, phrases, interests, anything.
I'll make an example with @WolfnightV4X1. Imma nickname them... LupusAngelicus, because why the hell not
Edit: If anyone wants to tell me how to mention users they're more than welcome to