Sun showers and freezing rain
Something I've wanted to do for quite a while now: shoot rain at 1/1000 to 1/2000 of a second to "stop" the raindrops in mid-air. Yeah, that Neo vs. Smith fight in the rain (The Matrix Revolutions) made quite an impression on me.
Lighting had always been the primary constraint since rain typically came with rainclouds (i.e. less light meant slower shutter speed for correct exposure, which meant that raindrops would appear as streaks instead of distinct droplets in the the captured photograph).
I've been thinking that the shot would have required a cumbersome artificial lighting setup to allow fast shutter speeds, but we were fortunate enough to witness a rare instance of light sunshower this afternoon.