"True dat" and people over 40 saying "my bad".
I can't help but say "my bad" sometimes, but I grew up saying. I agree that anybody over 40 saying it is strange.
I have noticed that a lot of the phrases mentioned are really just a generational thing. That's one reason I don't let phrases that I don't use bother me. If you didn't grow up in that generation you probably shouldn't be saying it though.
A lot of older people I work with refer to black people as "colored", and I don't mind because that's just a term they grew up with. It's not a term meant to be negative the way the n-word is. On the other hand, a friend of mine uses the term colored, and he's only in his 30s. The fact that he is black makes it even stranger.
EDIT: I probably could have made this post a lot shorter by saying "True dat."