Metal blade - Perhaps scissors or like, a single half of scissors- or a sharp pencil
Grip pad - Eraser
Saw - those things used for measuring angles (Protractors?)
crossbow - saw someone suggest a cardboard frame with a rubberband for a rope, That's pretty cool
Cannon - straw with paper wads, or a slingshot
Water cannon - some sort of drink container- like a water bottle (this would make the most sense), or perhaps a can
Wing panel - same sort of thing as wing
Balloon - those oragami paper balloons you can make
Spike ball - cardboard ball with nails or pencils or something sticking out
holder, half pipe, and plough - made of toothpicks or cardboard
remote grenade - rubberband ball