I'll nominate "As you know" as either a tie or close second.
It's literally telling someone you're about to share something they already know, and you know you're about to do it.
I like this, too many useless sayings
Keeps me up at night, man.
You know what I mean.
Nevertheless, that couldn't be true.
I'll raise you, ‘as per my previous email'
that one always gets me