There's a lot of cool anime characters out there who I'd want to be friends with. But I think this award goes to...

The Undertaker from Black Butler!

The Undertaker (aka Adrien Crevan) is the wacky sees-everything ex-grim reaper character of Black Butler who will only say useful things if you tell him a joke. His clever and cunning methods make him the antagonist of the story, but he does not have any motives to ruin anyone's lives unless it's time for them to die. He even runs a coffin shop and keeps track of people's deaths.

While I'm not huge into his hobby of packing dead bodies up for coffin transport, I wish I knew more about his character. And I wouldn't mind picking up a few of his joke and optimistic rambling methods.

Honourable Mentions:

[Left] Saitama (One Punch Man)
[Right] Genos (One Punch Man)