With the holidays right around the corner, why not grab a simple deep groove ball bearing and stack steel balls of descending sizes, top it off with a nut and washer "top hat", and you could even attach bobby pins as arms. There you have a festive snowman to place on the mantle, or as table decor.
If you're looking to make a unique card for the mechanically inclined guy (or gal!) in your life, consider using ball bearing stencils or patterned backing papers available via Crafty Ferret.
Super into fitness? You can make your own jump rope with just a few simple items and steps. Directions here: http://www.instructables.com/id/Jump-rope-with-ball-bearings/
(ADULT SUPERVISION REQUIRED.)
It's easy to make a kit (under $5!) to clean your bearings- especially for those of you who enjoy riding your skateboard or longboard. The best part about this one is that you may already have some of the materials needed at home.
Instructions here: http://www.instructables.com/id/Make-a-Longboard-Bearings-Cleaning-Kit-Under-5-in-/?ALLSTEPS
If you're particularly mechanically inclined, take a jab at this DIY camera slider. Total cost is under $100, and the photographer in your life would certainly enjoy this handy accessory.
Instructions here: https://camera47.wordpress.com/2014/11/04/diy-slider-with-bearings-for-under-100/