These are just a few of the more common customizations. One day at the game will show you far more variants than could ever be covered here.
Club Becomes AxeAn axe is just a club with a hunk of open-cell foam for a blade. The square marked on the block of foam pictured is the maximum size for an axe blade, which I decided to cut down to a more wieldy size and shape.
I used nylon strapping tape to secure the blade to the haft. Strapping tape is about the same thickness as duct tape, but it makes a much stronger connection because it won't tear. You want as little tape on the blade as possible, and three pieces of strapping tape are as good as several hunks of duct tape here.
Note that I moved the blade a few inches down the haft; you can't secure the blade to the thrusting tip.
Curved BladePVC pipe can be easily bent with a little heat. Boiling water is enough to shape it easily, but getting a tub big enough for your 50" katana isn't easy.
An alternative is to heat it over a stove. Practice on some scrap pieces first. You're most often going to overheat a small length of the pipe, resulting in an ugly kink in the middle instead of the graceful curve along the length of the blade.
Note: PVC both melts and burns. Attempt this over a gas burner at your peril.
For more detailed instructions, see Blake Deakin's Curved Weapon Tutorial.
Basket HiltThe simplest way to make a basket hilt is to cut a cylinder of pipe insulation into strips, and cover them with duct tape. Leave about two inches of tape past each end, then attach them to the pommel and crossguard of the sword. Wrap a band of duct tape to secure the ends to the sword.
Basket hilts can be a maximum of 4" wide, and they must leave enough room for you to quickly drop the weapon without getting in the way.
Thumb NotchA thumb notch can help you control your weapon by laying your thumb straight along the length of the pipe. This is especially helpful for a weapon with a heavy axe or mace head on the end.
As with everything, start by planning where it's going to go. Grip the weapon normally, then trace where you want your thumb to rest. (I did this while I was making the club, obviously. After the pipe insulation is secure is a good time.)
Cover with duct tape along with the rest of the weapon. You'll need to cut extra pieces to fill in the gap and secure it all to the grip. You could add this after the weapon is completed, but it would be messy.