'Course there is my personal favourite, thermite! it's so funny to sit a ciggarette sized lump of it in a tree and then introduce a magnesium fuse and a match, the whole tree burns down!
napalm is always fun to, and there are SOOOO many ways of making it,
- Dissolve polythene 'penuts' in petrol
- Fairy liquid and petrol
- Soap suds and petrol
etc.
I can testify Seph's scar- it was a big nasty brown mark last time i saw it!
P.s. There is always the fun of throwing a fist sized chunk of rubidium form the lab store at school into a lake, BOOM! not that i ever did that.....