Here is my "Low end" reference list.
Opera:
Rigoletto, Act 1 scene 2, duet with Rigoletto and Sparafucile (the Baritone) "vecchio maledivami"
Pagliacci, End of act 1, the instrumental conclusion after the aria "Vesti la giubba". It ends on a low note, setting the tone for things to come in act II.
Jazz:
Kind of Blue, blue in green, Paul Chambers concludes the track by playing the bass with a bow. This is only really evident on a system with tight bass.
Electronic:
Shuttle, Tunnel, on Ninja Tune records. This is a slowed down drum and bass style (UK grime without the rapping) track.
Pop/Rock:
Sarah Mclachlan, on the Album surfacing, the track "I love you". The baseline is very low and has tendency to come accross very muddled (if at all) on poorly set-up systems.
Blue Rodeo, 5 days in May. Featuring Sarah McLachlan on back-up vocals (not that this is relevant).
Hip-hop:
Digable Planets, their second Album, the track "Cool Like That". There is a second baseline (accent) that only comes in at certain points, again it is low frequency and is not apparent on most systems. It plays over the main baseline, so it has tendancy to get lost if the system cannot provided sufficent low end definition (more of a room thing really).
Well those are my picks.
I can't wait to check out Learsfools Wagner suggestion.