Suprisingly, creepers have rarely scared me.
#1: GVH11, Hollywood Holocaust
I was playing as Jitterskull in the {Obsidian-UK} GVH server (Team LMS, IIRC) and I was inside the lobby of the building. Then the door (which I was facing) opens and out comes a marine who shotguns me on the spot, killing me.
I'll update with more as I play.