4e's Retractable Arm Blade. (Way of the Samurai)
that thing has a reach of 1 and I always wondered how you could implant an aproximately 1 Meter long Blade in the Arm without getting difficulties in bending the Arm at the Elbow.
Either you can't bend the Arm anymore or you need to implant a two-part-Blade that you have to link when it pops out. But when you have a Blade made of 2 pieces its bound to break at the connection point. ImO its not a good Idea to have a Sword with a rated Break Point

And a solid, strait Blade is impossible to be planted in a Human Arm (no Problem in a Troll Arm though) if you want to keep your Elbow working.
a Spur otoh is just as long as your Elbow and thus you can implant two of them (one popping out in Front and one in the Back)
with a rated Point of Dance
Medicineman