In MGS3 (set in the Cold War era) there were no c4s, however it was a moldable prototype called c3, EVA made in into a butterfly for him before they split up from the cave, he used that c3 (the one EVA made into a butterfly) as the last explosive to be planted in the hangar of the Shagohad.
I believe she molded it into a heart. Snake molded it into a "butterfly," moth actually (If I remember correctly), himself.
Spoilers for those who haven't played MGS3
Partway through the game Naked Snake (aka Big Boss) loses his right eye. This of course compromises his depth perception. While recovering next to a fire Snake tries to brag a moth out of the air but can't do to his recently lost right eye. Later when he's about to plant the last explosive to try and destroy the Shagohad, he pulls out he C3 Eva had molded into a heart, molds it into a moth tosses it into the air and catches it saying something like "Gotcha now."