Gintama for comedy, Reborn for action.
Well, both of them start pretty badly, for a few tens of episodes. Or chapters.
Gintama starts with comedy and stays with comedy, but in my opinion the comedy simply gets a lot better. It's the only manga that has made me laugh so much that my stomach hurts... along with Cromartie High School.
There's also a few longer action and drama arcs.
Reborn starts with comedy, which in my opinion is absolutely horrible, but I believe it gets a lot better when the action comes in.
yeah, I haven't read Reborn past the comedy part. Maybe I'll pick it up later.
I recommend reading/watching them both :p