Some of the heaviest ones I've heard are
- Full Russian by xKore
- Magnum by xKore
- Pump It Up by Zomboy
- Fire Hive by Knife Party
- Rock N' Roll by Skrillex
And The Absolute heaviest:
- Forgive Me by Document One
Honestly, I don't really like the drop in that song, but you gotta give it credit, it's really really big.
Also, a lot of people seem to think that Sweety Man by Ry Legit has a huge drop, but I really don't agree at all, but hey, you should check it out and determine what you think for yourself.
If we're talking about FAVORITE drops, then mine would either be Promises by Nero (Nero & Skrillex Remix) or To The Stars by Modestep, (Break The Noise & The Autobots Remix)
They're all pretty philthy, you should check them out
My iTunes library