A few years ago ago, in the Fortean Times (a magazine that collects "weird news" from around the world), I read a brief article in their "Strange Deaths" section. Apparently a Vietnamese man sneaked up on his wife and tickled her from behind. Unfortunately for him, she was cutting wood at the time, and she reflexively spun around and hit him with the axe, killing him.
So, folks, be careful with those sneak tickles...