No contest: Instant noodles.

15 cent instant ramen is the sole reason me and millions of other poor people the world over don't have to mug you to pay for our grocereys.

Instant noodles kept me from a life of crime.

...Manga, anime, and Japanese Porn would be a close tie for second--without those to keep me occupied I'd have gone on a psychotic rampage years ago.

[edit]WTF? Wasn't this a thread about Japanese contributions to society? How'd this turn into a discussion of Catholic upbringing?

*sigh* The pope dies and suddenly this $hit takes over the internet[/edit]