These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Black Sheep Hit / Canon Discontinuity / Creator Backlash: Their cover of "The Saint" (for the film of the same name) is their biggest hit. It does not appear on any of their "best of" compilations and is unlikely ever to feature in their live set again after the very few times it was played around the time it was a hit. In fact, Canon Discontinuity applies to their soundtrack work in general, which tends not to get reissued, played live or have its existence acknowledged once it's served its purpose—"Satan Spawn" is an exception.
Fanon Discontinuity: Most fans prefer to pretend that the collaboration with David Gray, "Illuminate", never happened. Some would also deny the existence of the parent album, The Altogether.
Signature Song: Probably "Chime", which is still played at every gig. Other possibilities include "Lush", "Halcyon", "Petrol" and "Satan".
Tear Jerker: "One Perfect Sunrise", especially since it was supposed to be their swan song.
They Wasted a Perfectly Good Plot: The fandom rejoiced when it was announced Sparks would be collaborating on a track with Orbital. The fandom was disappointed when the result of that collaboration turned out to be "Acid Pants".