Another vote for a boa. If you don't want to risk ending up with a 9-10 foot BCI (not likely, but possible) then there are smaller locality boas like Caulker Cay or Tarahumara BCI's, Dumerils which have a reputation for being very laid-back and manageable, Brazilian Rainbow boas which are awesome once they outgrow their baby nippiness/defensiveness, etc.