I was a really easy to scare child.
I remember being like 6 or 7 and being really afraid to swim to the far end of the pool alone while taking swimming lessons, because this Yu-Gi-Oh card would always pop into my head.
Also, does anyone else remembers this final boss from a shmup called Strikers 1945 2? I recently discovered it was not some weird nightmare I had as a kid.
Needles, but that's kinda normal, apart from that i was terrified of firebugs, ice cream truck music and the Radiohead bear. Two of these is still scaring me at 29 but i'll let you guess which ones.