Have you created anything "home-made" for your plane? (or a low cost alternative?)

As a new pilot and new owner of a cessna 172, I've noticed the
seeimingly unlimited amount of accessories available for my plane. Most
seem to have one thing in common - a high price tag.

I was wondering if anyone reading this thread would share information
on any devices that are perhaps homemade or are low cost alternatives
to items available in aviation catalogs.

I guess this would include anything from pilot -assist devices to low
cost alternatives to lighting, interior upholstery, and the like.

Thanks in advance for any input you may offer.

Andy.