For me that was Smalltalk. The environment, the tooling, the purity of the language. Not saying everything is great there, but it's pretty great once you get us

For me that was Smalltalk. The environment, the tooling, the purity of the language. Not saying everything is great there, but it's pretty great once you get used to it. Seaside as a completely different approach on how to develop web applications which turns your thinking upside down when you are used to a typical request-response workflow. Django as a godsaint after working on a medium-sized pure-php project without any clear structuring.