I have three, and all are seriously NOT RECOMMENDED!- for various safety reasons:
1. "Blue Rocket"-drink up a GLASS bottle of whiskey(more people are better for this, because few people cause few to get to the empty bottle stage, and those who do regret it in the morning...). turn off ALL lights, cap the empty bottle. heat the bottle over the campfire until its just short of "too uncomfortable" to hold any longer, quickly uncap bottle and light the vaporised alcohol..the flame will shoot from the mouth of the bottle and make an interesting sound, as the vapor burns the flame usually sucks back into the bottle and creates very neat patterns of flame inside.
2. "Dripper" -this one was invented back before we knew of the TOXIC gases given off by melted plastic- also burning liquid plastic will stick to skin and burn extremely painfully.... don't do it...take any plastic straws, bags, or trash and set them alight in the campfire on the end of a long stick, when they are lit raise stick up as far as possible, the plastic burning will drip down still burning and look really neat, as well as making a VVWWEETTHH! sound as it falls.
3. "Marlboro Man Fireworks"-this is the oldest and crudest- invite at least on person who smokes, and bring a slingshot. When the smoker has finished their cancer stick, shoot it from the slingshot at any handy tree or solid surface- in my misspent youth this was only done when the solid surface was over someones head ( a teardrop hatch comes to mind, though I would NEVER do such a thing in light of my hard acquired, age induced wisdom ...)