Computers, electronics, and lasers.
My Lasers:
DIY LOC rkcstr 350ma in a flashlight host
DIY LCC microflex 480ma in a Dorcy host
DIY PHR-803T rkcstr 125ma in a flashlight host
DIY PHR-803T microflex 90ma in a flashlight host
O-LIKE 532nm 150mw module in a host