The Immunity Syndrome had a space amoeba that had to be traveling at warp in order to eat multiple star systems over a few days. Obsession has a cloud that traveled at warp...
I've got to admit that I always hated that so much that in Tin Man
I made a deliberate attempt to retcon it by having Data say "As no known natural phenomenon can travel at warp velocity, there are but two possibilities..."
Yeah, I introduced a continuity error into canon on purpose.