In Japan, the hand can be used like a knife.
[Dial Media; Ginsu television ad]
To show the obvious strengths of their mighty Ginsu knife set, Dial Media demonstrated a person karate-chopping some boards, then attempting to karate-chop a tomato:
In Japan, hands are used like a knife, but you cant cut a tomato with them!
And we all saw, right there, as a nation, that our hands would be completely useless to us as cutting implements. Used primarily to end anyones sentence that begins with In Japan ... Also used immediately after demonstrating physical prowess, which in this day and age means youve just yanked the lid off a stubborn jar of mayo or something. If you dont remember this commercial, then you probably were off reading books during your precious youth, you poor schlub.
See also But you wouldnt want to! and But wait, theres more!
– Jeff Stendec (February 11, 1994)
YouTube: Ginsu 2000
(This, I believe, is unfortunately a later version of the commercial with a new calmer VO etc)
Wikipedia: Ginsu