Best LPs to Test Turntables

The Telarc 1812 Overture with real cannons is excellent for tracking and dynamic testing.

I also concur with Brothers in Arms

Sorry. Reading through the responses was slightly depressing: most (though not all) of the recommended LPs are really SO unimaginative, so expected and all the usual suspects are there  -- ZZZzzzzz. Yeah, yeah, "it's to test the gear not the music" blah blah. But come on guys, let's get creative here! Something "left field" that the HiFi salesperson hasn't considered or demoed before.
A good general rule is: Anything played at a HiFi show is best avoided imo (D.Krall, V. Fernandez etc ... gawd.help.me). I'd prefer to listen to The Shaggs than anything by Ms. Krall.

I'll give you 3 vinyl goodies that will stretch any deck that you won't hear at any show or be found in any HiFi shop collection:

1. Frankie Goes To Hollywood's 12" single of "Two Tribes" Carnage Mix. It's got the kitchen sink in it [a Trevor Horn production]. Yes, it has those sharp-edged 80's samples BUT it stress-tests the pace and timing of a deck like nothing I heard - but mainly it tests SEPARATION. If your deck can isolate each element locked in those grooves and doesn't sound "mushy" then you got a winner.
2. Hawkwind "Warrior On The Edge Of Time" - start on side 1, track 1 and just play the bugger through to the end. Huge soundstage. Partly mixed while the band were tripping, but if the deck makes it sound magnificent (which it is) then get it.
3. Sunn O))) "Black One" or "Altar" ... the B-A-S-S. An aural assault (an acquired taste) but it'll put your deck through the mill that's for sure. I don't care for Sunn O))) myself but to stress a deck they're great. Herb Reichert can attest to that.
   

And as a bonus disc, anything by Whitehouse will work wonders. Musically it's awful harsh noise with no musically redeeming qualities whatsoever. BUT it is guaranteed to clear out any listening room - after which you can then play the above three without interruption.(The New Blockaders also work well in this regard - the Rough Trade shop in UK used to play them when the store got too crowded [ahhh, ye goode olde days], always cleared it out to all but the most battle-hardened).

You have to listen to some of your favorites critically. Songs you love; but break them down for what it is that you love. Listen to cymbals, vocals, piano, violin & Cello, kick drums or tympani, soundstage, and the totality of fun and beauty. Some albums will emerge as beacons.
If you have any of these, give 'em a try:

Broken English, Marrianne Faithful
Hasten Down The Wind, Linda Ronstadt
The Other Side Of Desire. Rickie Lee Jones
Pirates,  Rickie Lee Jones
Takin' My Time - Bonnie Raitt
Living and Dying in 3.4 Time, Jimmy Buffett
So, Peter Gabriel
Whites off Earth or anything by Cowboy Junkies

Another good test is to compare tracks with complex background vocals or lead overdubs and see if you can pick out the different vocalists.

If you're not in your own house listening to your own system, then you are "testing" not just a turntable in isolation but also everything else in the chain, including the room.  If you are not already familiar with these ancillaries, then it would be very hard indeed to judge the turntable.  But as to LPs, I would cast my vote with LPs that you already know very well and like on your own system, plus a few that are "iffy" in your own system.  I find that true upgrades to my phono system often make recordings that I had previously thought to be mediocre sound much better and sometimes great. 

I'll come back with specific LPs, once I can get to LP collection to write down titles.  Right now, I can only remember artists and labels.

Thanks everyone for the great suggestions.  They are really helpful.  I am having to get over a hurdle. Some turntables that I "listen" to I hear the motor.  I listen without music playing, just for the turntable itself.  I listened to the McIntosh MC5 this weekend, and the motor was really noticeable.  I turned it up to 78 rpms and it was really loud, IMO.  Then I listened to the McIntoch MC10, and no sound at all.  I'm trying to find someone around town who has ClearAudio turntables on display so I can "listen" to them.  The quest continues.