OK, so last night I was playing VF5 with my sweet ass new Hori turbo pad, which is fantastic except for crappy triggers, but whatever:

I finally reached MASTER rank with my Sarah, and was like "Hmm I kinda wanna start tanking up my Aoi and get her sexxi outfits but I don't wanna fight through a billion AI scrubs to get there," so I took the Hori, set the "A" button to the fastest turbo setting, and then rubber-banded it down. Within 3 hours I was at 3rd Dan ranking. (Note that tournaments will sometimes occur, breaking the automated button-mashing flow).
Now I am wondering what other games can give forth their bountiful Achievements with the equivalent of a hyperactive 5-year-old mashing the "A" button for hours on end.