Much in the same vein, but less of a toy, Tinymonth [0] has binary calendars - you just click on a day to toggle if it's part of an event or not. No .ics export that would really make it perfect, but it still seems extremely convenient in certain use cases.

Oh, and also from Postlight's labs, Textmoji [1] is a cute generator of custom emojis for Slack or Discord or whatnot.

[0] https://tinymonth.com/ [1] https://textmoji.app/