Wool

In my opinion wool is the best for any conditions.  It is warm when it's cold, warm when it's wet, cool when it's hot, resists rain and soiling (natural oils).  It masks the human scent and it's bug-proof.  It is quiet when going through the bush.  It's natural and not intrusively colored.  Wool takes a little while to dry and a little bulky, but it is durable and reliable.