Krypto (New-52, Pre or Post-Crisis)

Pre-Crisis Supergirl

Pre-Crisis Jimmy Olsen

Matrix

Guardian

Steel

Any others I forgot?

Krypto ^_^

It’s always Krypto

Easily Krypto.

@xenonyte: @saint_wildcard: @claymore1998: Then who's your second favorite?

The dog is great, but unlike Supergirl he can't kick ass and look damn fine in a miniskirt ;)

N52 Krypto to be exact. Krypto makes Kal more human, Supergirl and Jimmy only make writers turn Superman into a holier than thou patriarch who is right because he's right and never wrong.

@night4345: I quite like Steel for some reason. I liked him in the Batman/Superman annual.

Captain Marvel. I think he was a sidekick at one point.

Somebody get this dog an ongoing.

If Klarion the Witchboy can get one, I at least think Krypto can get a back-up.

Batman…

Alright, kidding. Pre-New-52 – never actually cared about this question, New-52 – Krypto totally deserves such title.

I love all of this characters. It is hard to choose between Supergirl and Jimmy Olsen but for me it has to be Jimmy Olsen. For god sake if you read Superman's Pal Jimmy Olsen, Jimmy have great adventures and he save the world many times. How I wish DC will do another type of Silver Age Jimmy Olsen story

Batman is his unofficial sidekick, and superboy is his official sidekick

Actually none of the above. If you look at current stories and past stories his major, I wont say sidekick, but partner in the good fight was and always has been Batman.

Superman never really had a sidekick, he has only been a mentor to all those characters you refered.

Hence why I put ' marks on sidekick.

Krypto