This Mk.5 Shiny Knife DIY kit is an entry-level electronics project.  All of the components to build your own prop LED knife are included:
 
Raw black PLA+ handle and belt clip parts (minimal support removal is required)
Clear acrylic blade of your choice
(2) LEDs of your choice (only the most effective color choices are available)
Electronic components (switch, battery clip, CR2032 battery)
Hardware ([3] M4 brass insert nut, [3] M4x10 flathead machine screw)
 
Tools required:
Soldering iron + small diameter solder
Wire strippers
CA glue (+accelerant  recommended)
2.5mm hex wrench
(optional) Rustoleum Truck Bed Coating spray paint
 
Step by step video available here.
 
If you order more than one kit, additional assorted LEDs will be included.  Extra blades are also available here.