Not sure if there IS a weapon creation template. You could base it on others.
Owner:
Weapon Name:
Type: Parasite or Weapon
How it is activated:
Level 1:
Description: Before activation
Activated: After activation
Finishing Attack:
Example, Allen's Cross Grave
Level 2 (not neccessary bcos you're not going to use it till you've leveled, but one can get it ready all the same.)
Description: B4 activation
Attack : After activation
Finishing ATtack:
same as above