Acid Rain and Another Dimension by Liquid Tension Experiment, and Prophets of War and Panic Attack by Dream Theater.
I usually play as Eraser (and I don't suck completely) and in all of those songs there were many times where I just had to retreat into the side lanes to stop my columns from overfilling in 5 seconds.
Panic Attack was probably the craziest of those.
I'm just waiting for the song limit to be stretched out to 20 mins or so (higher would be nice!) so I can give Home, Instrumedly, and The Glass Prison a crack. Damn, am I looking forward to those.