So what do you guys do when you play and the Nexus is about to explode? Do Zhonya's?
When I play Ziggs, I ult right on top of the enemy Nexus, so when it explodes, my bomb will explode as well so it's a double-splosion. (Hopefully)
When I play Rumble, I start backing right after I put down the Equalizer, to make a dramatic entrance that will pierce the skies and punch the stars.
Oh, you haven't seen true glory.
Surrendering just as the nexus falls, for a genuine double explosion. Nocturne ult, global and ends the game on a spooky note. Zhonyas at fountain just as an adc spawns, sometimes resulting in a post game death. Summoner ghost + dance. The visual effects never wear off.
Don't waste your potential with material explosions, it's all about the presentation c:
(Hang on, do you Zhonyas and then ult as Ziggs, and so the explosion comes out much later? Oh, you keep doing that.)
Post-game you become invulnerable.
Obviously, you 
ulti onto fountain.
