Lua
Lightweight scripting language from PUC-Rio, Brazil (1993) — designed to be embedded in other applications. ~100 KB binary, pure ANSI C, MIT licence.
Dynamically typed, first-class functions, a single data structure (table — hybrid array/hash). Coroutines, lexical scoping, no classes but prototype tricks work. LuaJIT (Mike Pall) is one of the fastest dynamic runtimes in the world.
Powers World of Warcraft addons, Roblox, Adobe Lightroom plugins, Nginx (OpenResty), Redis scripting, Wireshark filters, Neovim configs. Spotting Lua in a product = knowing it was written by people who value simplicity.