I can't see why breath of the blue dragon would be nonsensical... but I love Internal Combustion. Probably the best way to die.
Separate the energies of fire to unleash thunder... With your teeth!

Now that I did two of each elements, I'll expand! It could be fun if some of these end up in the PDF, but we need much more. Come to me, my benders! Create crazy forms of dealing death!

P.S.: I will classify the forms in spoiler blocks in the OP.