This cannot really hurt you, but anyway if you get hurt it isnt my responsiblity

A party popper
A drinking straw
Some bluetack

What to do :
1. Take the scissors and cut off the top of the party popper
you can do what you want with the bottom, keep the part you cut off.
2. Take the straw, and stretch it out and cut the part thats just before the bumpy part.
3.Take the blue tack and rip a bit of bluetack and roll it into a ball.
4. Then put the ball on the end of the straw
5. Mold a cone shape
6.Take the tape and cut off a bit of it and wrap it around the end of the straw near where the bluetack is
7.Take the bluetack and roll it into a sausage
8.Get the straw with the end tape and take the party popper off and slide it in the middle of the straw
9. Making sure the cardboard is in the middle of the straw
10. Take the rolled up bluetack and wrap it around where the straw and the party popper meet.
11. Make sure that it can come off.
12. Pull on the string and the straw will fire! ;D

have fun