Johannes Krauser II (Detroit Metal City), we would rock the hell out and destroy stuff together :3
also Okabe Rintarou (Steins;Gate), I would be his mad assistant and we would go to the past and see our own births (wait that sounds kinda wrong...) anyway we would also make gel bananas for everyone (sounds wrong too...) XD
I'll summon one of the scientists from Toaru Majutsu no Index so he can give me Esper powers =D. Hopefully I have talent, I would rather risk it than trying to summon someone to teach me magic because I hate magic.
To just hang out and have a fun night on the town I would probably summon Akio Furukawa. However Nyaruko the Crawling Chaos would be fun to watch anime with and she could explain the mysteries of the universe to me.