C4
The C4 is Solid Snake's Down B move confirmed at the Smash Bros. DOJO!!. Snake places a C4 on the ground and may detonate it at any distance by pressing the button again. When Snake detonates it, he flourishes the remote detonator, and exclaims "Now!" as he presses the button.Note: When you hear Snake say "now!", RUN!
Snakes down Smash acts in the same way except it explodes when someone walks on it (like a motion sensor).
You can place a C4 on your opponents. It acts similar to a gooey bomb in that it can be passed from person to person when they get near each other. When you play a C4 on Zero Suit Samus it may be in the shape of a butterfly like in Metal Gear Solid 3.
Origin
C4 is a powerful plastic explosive that can be modeled like clay into various shapes. It is incapable of being detonated by anything other than the detonator itself. C4 has always been a widely used tool by Snake and is one of the weapons that is required to progress through the game.