This morning I challenged myself to get as close as I could to recreating the sound of the "seagulls" in the song "Tomorrow Never Knows" by The Beatles. I tried several different pieces of software and then ended up using an app on my iPad called PixelWave. With a little messing around I came pretty close (well, close enough, I've got clients waiting on sounds) and I was satisfied with the results.
I do these kinds of audio exercises regularly because not only is it fun, but it also keeps my on my aural toes, not to mention that I've got a pretty big... library of sound effects. So there's that.