For some unknown reason this brand new extension cord is busted, many people would toss this in the trash at this point. I noticed that plugs kept slipping out of there sockets when in use, then the contact between the sockets and plugs would only allow juice to flow when positioned upside down WTF! At worst I could snip the splitter off and have a spare replacement or patch cable, apparently the problem is in the splitter.
Tools and Materials
Flat head screw driver
Cordless drill
3/16 inch heat shrink tubing
Pliers
Needle nose pliers
Utility knife
Heat gun
Two small screws

Step 1: Open It

This took around three minutes to pry open. I wedged pliers to into the gap and popped its seal, with only minor scratches on the exterior. The problem was a few loose contacts made from thin gauge copper (cheap), the emerging problem is how to put this back together. I decide to modify it just a little, with the addition of heat shrink tubing as reinforcement at its stress location nearest to the wire terminal. I'm only interested in repair, although the extra tubing should prevent stress, the plug end already has it. Here's a list of modifications possible.

Aesthetic sleeve or cable management system
turn switch
A different plug (flat, angled or industrial)
Permanent soldered wire terminals
See this instructable for numerous ideas.

Step 2: Reinforcement

Cut some of your heat shrink tubingÂ. The contacts keep me from slipping the heat shrink over them. Slowly stretch the tubing with needle nose pliers till it can slip over this. First the reinforcement tube slides on, then two more little pieces to cover the exposed wire. Break out a heat gun or a hair dryer and shrink it.

Step 3: Fix It

Pinch the copper flanges close together with your pliers, this will make the connection tight. Make sure flanges aren't pinched closed so the plug will still fit.

Step 4: Put It Together

Notice these small plastic pipe extrusions on the dye cast plastic. Two of them have cracks from when it was forcefully opened. The extrusions were probably glued together but they serve no purpose other than extra structure. The side that has them intact will become where the threaded screws will go. I found a drill bit that match this small hole, then two short screws that almost matched the drill bit diameter. First use a needle to make a pilot hole on the half with the busted extrusions. Make sure your drill bit doesn't extended longer than your screw, so it doesn't come through the other side. After this pick up your utility knife and carve the edges of the hole, so the screw will be recessed. Now screw it back together, use a spring clamp or vice to keep it sealed tight while you tighten the screw. Epoxy it closed if you don't plan on reopening it, but keep in mind that copper may bend again. If you're more anal than I am, paint the screw heads white with enamel. Now your done twenty minutes later, eight fifty saved.

Step 5: Extension Cord With Grounding Prong

This type of extension cord cannot simply be opened up, fixed and put back together. Unfortunately it requires replacing the entire plug. To do this properly soldering is necessary. Though it can be done with out soldering it will not hold the test of time.
The plug heads can be acquired at the hardware store. These are available in many varieties and usually will have directions on how to assemble them.
Tools and Materials
Flat head screw driver
plug head assembly
wire cutter or industrial wire stripper
Needle nose pliers
xacto knife
flux and resin solder
soldering iron