Favourite programming languages

Smalltalk and Lisp (Common Lisp) are my favourite programming languages. Apart from them, there are not many programming languages with:

A robust theoretical core. Smalltalk syntax fits in a post-card. Lisp has been described as the “Maxwell’s equations of software”. Both created quite a long time ago, with some very bright minds involved in their design.
Uniformity. In Smalltalk, all there is are classes and objects, and message passing between them; and that uniformity is reflected in the syntax too. In Lisp, code is data, and data is code, and everything looks like a list.
Interactive development. Both languages are image based. The image provides access to the running application, and there are no separate compile/run/debug phases. Both Smalltalk and Lisp provide the tools for live exploration, inspection, debugging, and much more.
Development of DSLs. Lisp is the best suited for this, as it provides macros. Smalltalk flexible syntax is good enough for developing embedded DSLs.