It's one of my favs but not quite nuraber one, Final Flash takes that spot, the build up to it was awesome and the move itself didn't disappoint, owned to f*ck Cell.
I've got to give this one to Kenshin's Amakaeru Ryu no Hirameki. It's his final attack. Pure badass.
Some honourable mentions:
There's a ninja called Jyubei Jimushi in Basilisk who has no lirabs. To avoid spoilers I won't give away what his technique is, although you can probably guess.
That comic relief character in Bleach who shoots slippery muccous. That technique cracked me up.
I worthy contender but you can't beat the shining finger! the name alone radiates awesomeness and hilarity all in one, to bad it wasn't a middle finger strike though that would make it even better.