What's your favorite sandwich and why?

Geek Question of the Day: OK so this one might not be as intrinsically geeky as a lot of other questions I ask, but I'm curious; What's your favorite sandwich and why? Obviously anything works and feel free to broaden the definition of sandwich if you need to. This one was suggested by D.B. Fuller in our Slack!

Image source: http://bit.ly/2Xi9Ekc