Emojis make surprisingly good favicons. They are colorful, universally recognized, and render perfectly at small sizes. I have used emoji favicons on hackathon projects, personal sites, and client demos—they always get a smile.
Emojis are designed to be legible at small sizes—that is literally their job in messaging apps. A star emoji at 16x16 pixels is more recognizable than most custom icons at the same size. Plus, emojis have built-in semantic meaning: a rocket for a startup, a paint palette for a design tool, a gear for a settings page.
Use genfavicon.org and switch to Emoji mode. Pick from 20 preset emojis or type your own, choose a background color, and click Update Preview. Download all six favicon sizes as a ZIP. The emoji renders natively in your browser—no image upload, no server processing.