I took the pictures in bit of a rush, so the quality ain't best :/ But here's my O-matoran for the periodic contest. I'll keep on giving you language lesson here, as once more the name is the finnish word of the element ;) This was also bit of experimenting to not use ball joints. In the end he got only 4, on hands and ankles.
Happi has an unusual hand which emits oxygen. He has learned to use this for his advantage.
When Happi punches his hands together, they create a spark, which ignites the oxygen the other hand emits.
He can aim the born fire to a direction he wants to.