"When I think about how dumb I was as a teenager, I wish I could travel back in time and kick my own ass!"
"Actually, if you traveled back in time and encountered yourself, the space-time continuum and the universe itself would collapse."
I'm not talking about all uses of the word "actually" here, I'm talking about when people use it in response to a statement that's clearly meant as a joke. This comes from people who always feel like they have to have the last word, or otherwise "top" what you just said.
"When I think about how dumb I was as a teenager, I wish I could travel back in time and kick my own ass!"