Most likely:
curlywas (https://github.com/exoticorn/curlywas) -- c-like but very low-level; seems very complete; rust impl; mit license; short but seemingly thorough docs?
wa (https://github.com/wa-lang/wa) -- go-like, not clear how high/low level it is, thorough docs, seems promising, agpl license, lots of mandarin in docs
virgil (https://github.com/titzer/virgil) -- ruby-like? gc; cant find license; last commit 3 hours ago; thorough docs but all in md files in repo
assemblyscript (https://github.com/AssemblyScript/assemblyscript) -- typescript-like; apache 2 license, minimal runtime with gc; implemented in js
walt (https://github.com/ballercat/walt) -- JavaScript-like made for wasm, 25 contributors! decent looking docs, might actually be usable! most commits 7 years ago but last commit 3 years ago though, mit license
onyx (https://wasmer.io/posts/onyxlang-powered-by-wasmer, https://github.com/onyx-lang/onyx) -- ocaml-like? recent activity, full docs, bsd license, not sure if it has lower level capabilities or how much the higher level features cost at runtime or build time
waforth (https://github.com/remko/waforth) -- forth for wasm! upside is that its forth, downside is that its forth; mit license; great docs; seemingly inefficient due to constant lookups?
Less likely:
thinscript (https://github.com/evanw/thinscript) -- js-like with macros; abandoned 9 years ago; not yet licensed
wase (https://github.com/area9innovation/wase) -- C-like syntax but still wasm-like, not super recent but not super old, only a few contributors, not sure how complete it is but its docs give a feeling of being mostly-complete, MIT license
wam (https://github.com/kanaka/wam) -- wasm macro preprocessor, just one guy, last commit 7 years ago, very few built in macros, mozilla license (???)
wah (https://github.com/tmcw/wah) -- wasm but with infix, doesn't seem extensible with macros, two contributors, last commit 8 years ago, eclipse license (???)
Honorable mentions:
mini-c (https://github.com/maierfelix/mini-c) -- C to wasm compiler, seemingly abandoned 8 years ago, not sure how complete it is
c4wa (https://github.com/kign/c4wa) -- c to wasm compiler, no activity in 3 years, no license, written in java
P.S. You might have more success with replies on Reddit. HN is very all-or-nothing.
Zig produces extremely small, optimized WebAssembly modules. The language includes WebAssembly-specific built-ins like @wasmMemoryGrow, and its entire standard library offers first-class support for WebAssembly.
Zig can also optimize code for specific WebAssembly runtimes, making it, in my opinion, the most efficient WebAssembly compiler available today.