This isn't a new trick (it's over a decade old!), but it's still a good, clean look at a tactic that, while often outlawed competitively, is still awesome considering the teamwork and timing required.
(Below is a gfycat, so if you're on mobile and it's not auto-playing, just tap on the thumb and it will take you to the clip)
For history's sake, here's the famous 2006 move from Pubmasters that started it all.
It's worth noting that you won't see this trick at the upcoming ESL One event in Cologne though: de_nuke isn't part of the official map list, having fallen out of favour in tournaments for a while. Shame, really.