#5 is really nice. Couple of suggestions from our group. Can you flip the buffalo so it is facing the other direction? Also, can some of the lines be thicker and perhaps eliminate a few others so it becomes even more conceptual? Perhaps increase the size of the font a bit too.
If I were to see this on a shirt from a distance I would want to be able to read the word.
So far #5 has the most votes. And lastly, can you try it in the darker green color. I think the consensus is we like the green.