QuickJS is a really, really interesting engine because it's only ~200KB. Fits a lot of cases where you want to add scripting ability but without bulking out size unnecessarily. Unfortunately because it lacks stuff like JIT it'll never rival the likes of V8 in performance. But in terms of bang for buck it's unbeatable.
Luajit packs a similar punch, and actually has performance comparable with v8.
Plenty of things with performance and size similar to quickjs, though; regular lua, micropython, chibi scheme, s7 scheme...lots of great options.