Icons for Anything?

I tried searching for five things that I thought would be unlikely (like a tractor) – and in all five cases, there were multiple icons in the database.

These come from The Noun Project.  Here's their mission statement:

The Noun Project collects, organizes and adds to the highly recognizable symbols that form the world's visual language, so we may share them in a fun and meaningful way.

The contributors to this project sure put a lot of work into it!

All the icons are free, by the way.