This little rocket costs next to nothing and can achieve amazing altititudes.
All credit for this rocket should go to pudi.dk as his "ultimate straw rocket" gave me the idea for this one.
This is my first instructable, be as harsh as you see fit, all criticism is welcome but do be fair.

Step 1: Materials and Tools

Materials needed:

skinny straws(not flexy straws).
larger straws(still not flexy).
hot glue gun sticks.
tooth picks.
a BIC pen.

Tools needed

A foot pump.
A pair of scissors.
a skewer (for dismantling the pen).

Step 2: Destroying the Pen.

Get your BIC pen and take the ink tube and tip out aswell as the little blocker in the end(this is what the skewer is for just push it into the pen and push it against the blocker and it should pop out).

Step 3: Making the Launcher!!

Put the one of the big straws down the bic pen barrel( into the end we popped the blocker out of), make sure you push it far enough down so that it gets a little bit jammed, now cut it so that its flush with the end of the pen.
Get your glue gun going and put glue around the hole where the straw goes in to make sure it cant come out( this is shown in the really bad photo below) MAKE SURE YOU DO NOT COVER THE UND OF THE STRAW!!!!!!!!!!! only put a little bit of glue around so that it dousnt pop out when you launch it.

Step 4: Making the Rocket!!

OK now get your small straw, your bigger straw and your toothpick.
again get your glue gun going.
now pump some hot glue down the end of your small straw and while its still hot snap your tooth pick in two and shove one half into the hot glue.
now put some glue around the toothpick and wait for it to cool, when its cool enough roll glue around the toothpick so that you end up with a nice nose cone shape.
now cut a short length of big straw and slide it over your rocket until it hits the nosecone then put a bit of glue around it where it meets the nose and wait for it to cool.
tadaa it may not look like a rocket but it goes like you wouldn't believe.

Step 5: FIRE!!!

well thats about it, to fire the rocket place the rocket in the launcher (give it a good push so its a little bit stuck).
now put the launcher into the pump nozzle, clip the pump nozzle down( so that the launcher stays in).
now just put it on the lawn or whatever and either hold the launcher in your hand, put it under your foot or make a little launch pad thingy for it, and then give the foot pump a short sharp pump with your foot. you will be surprised @ how hight this little rocket can go.
video included...... i hope.
please comment.