Flocon
Snow on your desktop and window tops! Christmas spirit directly beamed into your Mac!! Shake a window to knock it off, or push it aside with the cursor. Christmas lights included :)
Download Flocon.dmg (macOS 14+, Intel and Apple Silicon) or see the source on GitHub. Flocon isn't signed with an Apple developer certificate (price is too steep for a little project like this...), so macOS will block it the first time. The steps are in the README.