Iceberger
How would that iceberg really float? Lots of illustrations that show "the $FOO iceberg" show a berg floating in an orientation that's very unlikely. This site lets you draw the vague outline and see how it might really end up.
Excalidraw
Simple online drawing tool that generates diagrams that appear to be hand-drawn.
jgraph/drawio: Source to www.draw.io
Client-side diagram drawing app. Open Source.