My 6 yr old son did that when he was a baby and grew out of it by the time he was 2. I too am/went (going) through this with my 10 month old son. My husband and i started a new game with him whenever he felt the need to head butt us, we would hold his head (gently) and rub our foreheads together with his. He now no longer head butts us and now we just do the head rub (we dont hold his head anylonger since he knows how to do it) It is like eskimo kissing or rubbing noses just with the forehead. This may not be a solution, but, it sure saved us from knots and headaches. We like it cuz its kinda affectionate. AND doesnt hurt
We also changed the fingers in the mouth thing (kinda) as well. this too is natural and many children do it. They just want to see what you have, what they have, what the difference is and so on. It is part of learning. I have started that when he does this, i point to his mouth and say "mouth" then, i continue around the face, next the nose, then eyes. to get him interested in the rest of the face and not concentrate just on the mouth. Not a solution either, but I figure if he is ready to explore alittle, I will help him learn and show him I am interested in his games/learning.