blowgun fights
Step 1: Take a biro, and remove the innards, leaving the plastic casing alone. Step 2: Nick an exercise book or two from the poorly-guarder stock cupboard. Step 3: Tear off small pieces, and soak in (your) mouth to form a ball. Step 4: Jam into the casing, and blow out of the narrow end at pretty high velocity. Step 5: Fire at will.
written by Ja*on C, approved by Log

I misguidedly invented 'Blowgun RISK' for our physics lessons. Based loosly on the game of the same name. You got points for attacking other 'continents' succesfully, ie winning a 'blowgun battle'. Other continents were other tables, The group of hard lads was obviously North America, the group of physics boffins was obviously Australasia. I spent ages working out elaborate rules. Unfortunately when I excitedly annouced our new activity to the rest of the class you can guess the painful result.
written by Jo*l A*der*on, approved by Log

Take the bit from the end of a shoelace. Fray out the lace, and push a pin through. You now have a small dart, which when launched through the trusty hollow biro will stick into someone's body (or, more amusingly, face) and hang there in a relatively painless way, giving them tetanus.
written by an*ny*ous *se*, approved by Log

Holding a thermometer in a bunsen flame for long enough will eventually cause the mercury to expand, break the glass and spurt out of the end. With practice, this can be aimed.
written by Ju*ian*Bur*ell, approved by Susan