Kanzenshuu

If dbz games count than "anything is possible"
from ultimate tenkichi

I loved Goku elbowing Recoome in the stomach and knocking him out. It was so cathartic and a little bit spine-chilling given how this is first time we see Goku in action since the end of the Saiyan arc and how much of a danger Recoome was to Vegeta, Gohan and Krillin.

Oh... and welcome to ...

Another favorite is when gohan punches frieze stomach in fusion reborn

When future 18 punches future tiens stomach is great too

Many great ones have been said already, but I really like Goku's gut punch to Freeza:
http://33.media.tumblr.com/b0c9eb6f92b088dac56b581d478441e1/tumblr_inline_n8nrtcj2dU1ri065t.gif
The full scene slows down the animation a bit, and it gives you a sense that after a long fight, Freeza is no ...

Mine is gohan kicking cell what's yours