I've never tipped anybody in Japan. I have, however, on occasion given someone who has regularly done something especially nice for me a small gift from the States or a box of sweets, etc.

In Japan, though, tipping for normal service (and even extraordinary service) isn't at all necessary. I've heard a story of a man who tried to tip the bellman at a hotel in Tokyo (forget which one). The bellman accepted the money, but at checkout, the man found that his tip had been deducted from his bill. The bellman didn't refuse the money, since that would be rude, but just took it down to the front desk and had them take it off the man's bill.