Clock movements and parts
One-foot USB extension cables (so common!)
Acrylics. Scrap bins in stores are a great resource.
Gobs of electronics.
Neodymium magnets. Check out their surplus items and eBay auctions for deals.
Printing & Cutting
Lasercut stencils. Never used, looks good.
Excellent full-color vinyl stickers with cheap die-cuts (batches of 1,000)
Stickers are decently priced, but don't have glossy coat that protects them.
Really great full-color, double-sided, round corner business cards
$20 for 250 b/w stickers, but delivery can take up to 8 weeks.
Great free remixed video game music