A brain teaser.

I am a 8 letter word.
My 2nd, 3rd & 4th letters spell an Animal.
My 4th, 5th, 6th, 7th & 8th letter is a Weapon.
My 1st, 2nd and 8th letter is used for writing Exams.
My 3rd & 4th letters are same.

Guess who am I ?