Gabester
From Super-wiki
Gabester is the mashup nickname used to refer to Gabriel aka The Trickster (portrayed by Richard Speight Jr.). The name came to being after the Trickster was revieled as the archangel Gabriel in 5.08 Changing Channels.
It is frequently used by the fandom and Richard himself.
In fandom the nickname can simply refer to Gabriel or to special moments in canon or fanfiction when he is being his typical Trickster self.