DOMPurify - a DOM-only, super-fast, uber-tolerant XSS sanitizer for HTML, MathML and SVG. DOMPurify works with a secure default, but offers a lot of configurability and hooks. Demo:

Client Side Prototype Pollution Scanner

Searcher for cross-site leaks (XS-Leaks)

CTF writeups

Legend Agar.io Mod

A JavaScript sandbox using proxies

Diep.io extension