For got to add:
Blue phase infernalis are probably one of my favorite Bay Area Thamnophis. In the wild, they are strikingly blue, almost the the extent of tetrataenia (I mean, they are technically the same species, and arguably, the same subspecies based on DNA genetics). The photographed was a large male (about 28 inches snout to tail tip) and was deep in shed. The specimens from that locality are BLUE when in their prime.

Atratus atratus are probably my favorite local species of Thamnophis. Occasionally I will see MASSIVE, almost gopher snake sized, Santa Cruz garters. Despite their common name of "Aquatic", I rarely find them near water. The burly looking one (head shot, first pic) was actually found at a site where I find California Mountain Kingsnakes (Lampropeltis zonata multifasciata)...far from any permanent water!

I'm gonna have to say my favorite North American Thamnophis right now has got to be the Oregon Red-Spotted. Gorgeous snake that I hope to work with some day. Would love a locality specific specimen...