.. or Kate Pierson from the B52's... we can sing harmonies together while we roam or visit the love shack :)
Wonder Woman, or Tiffanee! lol
An cyborg of some kind, because they can be programmed to be loyal... and they can self-repair!
otherwise, Johanna from Hunger games...
Heather Locklear. And I don't care if she would be of any help!
I'd take Clyde.
The list is huge, but I'll post only some: The Genie, Meeko and Flit, Timon and Pumba, Abu and the Magic carpet, Jiminy Cricket, Baymax, John Watson, Hermione Granger, Roronoa Zoro, Tony Tony Chopper, Happy (Fairy Tail), Riza Hawkeye, Genos (One Punch Man), Seras Victoria, Armin Arlert and so on.
Edit: Oh, I only focused on sidekicks to be my sidekicks... that's way too many choices to pick only one. I'll have an army.
Satori Komeiji from the PC game series called Touhou. She'd be able to read my opponent's mind using her third eye and tell me what they're planning to do. She has some fighting skills as well, which would be helpful. And I can't forget to mention that she's easy to look at.. well, at least in my opinion. lol