Thanks for the help everyone! Oldhat, I'd like to build stuff that can be used in an outdoor application without worry that it's going to rot or fray, from what I've read a quality linen thread and beeswax will hold up like there's no tomorrow, but the code sounded like it would add an extra level of protection and durability. I'm hesitant to use poly thread because of it's inherit slipperiness, I'm also wanting to hand-stitch, I really enjoy working with my hands.
I'm especially wanting to build some harnesses and collars for my hunting dogs. We go through all kinds of damp mud and muck, I clean and condition my leather on the regular but any additional measure of toughness can't hurt.
Theoretically, if I decided to use code, I could buy a waxed thread and then just wax it in addition? I'll be ordering some of this thread soon, which was recommended by another forum member: http://www.ebay.com/itm/221455736903?_trksid=p2060353.m1438.l2649&var=520324821693&ssPageName=STRK%3AMEBIDX%3AIT
I also found this seller with Barbour's for what seems like a very good price (considering trying it?):
http://www.ebay.com/itm/Barbours-Linen-Thread-/281715973986