Stunning Fist & Big Creatures?

[Darklone]

I do like the picture of a halfling kicking a giants shin. Btw, you can break the kneecap with a headbutt...

 

[Ferret]

If the halfling can hit a tendon on the back of the foot it should be enough. I know few places (on the body) where if you press hard enough it hurt a lot, such as the inside of the fore arm near the elbow, thats the funny bone.

If the hypothetical halfling can catch that properly the dragon cold very well be stunned.

That is if it can get past the dragons DR, remember it has to deal damage to get a chance.