Marshall is definitely the reacher. Look at the man.
Added:
In typical How I Met Your Mother style, we see a fake sequence of male Jenkins stripping. In reality, it was a much hotter Jenkins (Amanda Peet) doing it.
Added:

How I Met Your Mother Season 5 Episode 13 Quotes

So are you really a Vikings fan or was that a lie too?

Jenkins

Ted, I've been skee ball champ here since Law School.

Marshall