Brake fluid and chlorine (the kind you get for swimming pools). Best to maintain a distance after you mix it and not do it anywhere near anything you mind having razed.
If safety isn't a concern (meaning you have a method to ignite it, and can watch from a proper distance), I'd mix up a batch of thermite. Easy to make, and quite spectacular.
But, I think one of the better chemical reactions is to use ammonium dichromate (add in some magnesium shavings) - then light using a match. It is not really dangerous but you want to be in a ventilated area because the fumes are not the most healthy for you. It does not do the flowing lava thing but instead does a slow burn with flame and ash. That is what I used years ago for my model volcano.