Most colubrids are very nice
Corn snakes are very nice, fairly active, mostly terrestrial (mine aren't good climbers...), and easy care.
Another not well known colubrid is the Fox Snake, which is one of my favorites. It is arguably one of the most docile snakes, mine has never even attempted to bite me. They are terrestrial, arboreal, and aquatic, so they make very interesting captives.
Rat Snakes are also very good snakes with many color variants and are fairly docile.
Kingsnakes are also very good snakes, but never handle one after you've held another snake.
Rosy Boas and Kenyan Sand Boas are also good snakes. Both are relatively small, docile, and fairly easy to care for.
The Rainbow Boas are also very cool snakes, but when young they are a little snappy. Their caging requirements are a little more advanced, so if you plan to get one be prepared to provide a proper cage for it.
I haven't worked with many Pythons... but if you were willing to go over 6' Jungle Carpet Pythons are very cool snakes. They sit out when they are adults (most do) and make wonderful display animals. As young some are a little snappy, but most are docile.
Hope that helps
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Currently have:
0.1 Antherystic Elaphe guttata - Corn Snake
1.0 Elaphe vulpina gloydi - Eastern Fox Snake
1.1 Morelia Spilota Cheyni - Jungle Carpet Python
0.1 Leucistic Elaphe obsoleta linheimeri - Texas Ratsnake
Saving for:
Agkistrodon Contortix mokasen - Northern Copperhead