Favorite OP, because it's upbeat sexy jazz music is legitimately my ringtone. But more importantly, and something you don't see in the video I listed, is that Baccano! (much like Durarara!! after it) inserted the recaps into the OP. So not only is the OP useful for introducing and reminding you of the many characters in the series, but it'll keep you up to date with all the relevant information. I have no idea why more shows don't use this method.
Visually, it's going to mean nothing to y'all without the context from watching the show, but as someone who was watching the show, it gave me legitimately chills/goosebumps for the first twenty or so episodes it was used in. The gungi pieces with the snapshots of the characters part in particular. I also just love the song.