Scheme

The whole early MIT culture reflected in the MIT Scheme.

To do everything just right

Strong typing (type-tagged values)
Just a few special forms (lambda, define, cond, let)
Numeric tower (proper, “safe” math)
The List structure everywhere (biology-inspired uniformity)
Partial application can be implemented as a function
Proper macros (no accidental capturing of vars)
R5RS was the peak
OOP features were just a DSL (a library).
MIT Scheme is still alive and well. Serious, state-of-the-art engineering.
Chez Scheme is even better technologically

Records and Modules were notably missing from the standard.

Nowadays Racket is the state-of-the-art system.