Great thread! I made a list of around 40 things to do with each element at the beginning of the year. I have so far only done:

FIRE: Made an old lady caught on fire vaguely, made a small lighter-flame and made a red glowing mark.
WIND: Never tried it, does telekinesis and electrokinesis count?
EARTH: Never tried it.
WATER: Made some wet sand produce steam. Does skiiing on water with your feet only count?
ETHER: I've flown and teleported.
DARK: Mindcontrolled a guy into committing suicide with a knife. Also been evil.
LIGHT: Never tried it.
NATURE: Next on my list, make a tree which will produce dreamfruit.
SUMMONING: Summoned all kinds of stuff. No special creature or DC though.

That'ts what I've done. I really wanna learn how to control fire, but I seem to have problems visualizing it...