We've had different threads covering holy grails, worst titles, best picture quality etc, but I don't think I've seen one covering your all time favourite LDs.
You know what I mean....the ones you just keep returning to over and over again to play and never tire of!

For me personally it would be:

Bad English: The Videos [ESLU-80] - great melodic rock band formed from the remains of Journey and the Babys.
Beastie Boys: Compilation Reel (1987) [68LP-109] - contains one of the coolest music videos ever released on laserdisc 'She's On It'.
Chaka Khan: Live at Roxy (1981) [MP039-22MP] - very early Pioneer laserdisc which really shows off the superb capabilities of the format and of course captures Chaka Khan around the time of her classic "What Cha' Gonna Do for Me" album.
Duran Duran: Extraordinary World [TOLW-3164] - in my opinion 'The Wedding Album' was their finest hour. This LD remains unreleased on DVD and includes videos from the previous excellent album Liberty and interview footage.
Durutti Column: Domo Arigato - Live in Tokyo (1985) [COLY-3005] my all time personal favourite laserdisc - exquisite guitar playing and percussion throughout. Beautifully filmed and recorded. It does not get any better than this!
Foreigner: Super Rock '85 in Japan (1985) [LVB-2007] - Foreigner at the peak of their career.
Irene Cara: Fantastic Show (1982) [LNK-533] - striking cover art and really enjoyable Italian TV show featuring Irene around the time of her debut album just before she hit the big time.
Journey: American Tour '83 - Frontiers... And Beyond (1983) [TE-D037] - Steve Perry belting out all the most memorable Journey hits along with a detailed tour documentary. Remains unreleased on DVD.
Judas Priest: Live - Screaming for Vengeance Tour (1982) [96-4M-6] - One of the best live heavy metal concerts ever recorded.
New Order: Pumped Full of Drugs (1985) [78C58-6098] - The audio on this disc is stunning. I must have watched this a hundred times!
Olivia Newton-John: Soul Kiss (1985) [5112-9] - brief period in Olivia's career where she turned into a bona fide rock chick! Love the matching album as well. Contains exclusive interview footage. Reminds me of Heart circa 1985 with the big hair and synths!
Prefab Sprout: The Best of Prefab Sprout (1992) [ESLU-115] - always been a sprout fan so was over the moon to find there were actually 2 LDs available. This one features virtually all their videos and remains unreleased on DVD.
Rox Diamond: Live in Japan (1992) [FHLF-1053] - strong candidate for most underrated rock band ever. Beautiful melodic rock. If you liked Giuffria you would love this band as they are almost identical.
Saxon: Live Innocence! (1986) [SM058-3108] - 'Back on the streets again' was perhaps Saxon's best attempt at a commercial single. Great live concert and accompanying promo videos from the highly underrated 'innocence is no excuse' album.
Scritti Politti (1986) [SM048-3116] - another great music LD which is very difficult to locate. Videos are in CAV format and audio is crystal clear.
Siouxsie and the Banshees: Once Upon a Time (1981) [JM038-0049] - highlights are tracks like 'red light' with that sparse new wave synth sound and of course the classic 'spellbound'.
Survivor: Live in Japan (1985) [G78M0081] - their best album 'vital signs' live with a few extra tracks from 'eye of the tiger' and 'caught in the game' albums included as well. You cannot go wrong!
Swing Out Sister: It's Better To Watch +1 [POLS-1015] - great pure pop LD with stunning sound and picture. This re-issue features 1 extra track not included on the 1st edition pressing.
Talk Talk: It's My Life [JM034-0035] - little gem which is probably the rarest 8" JM series Western music LD released.
The Cult: Electric Love - The Videosingles [TFLR-78515] - who would not want to own classic rock tracks like 'she sells sanctuary', love', 'wild flower' etc on laserdisc?

So what are your favourites and why?

Hmmm . . . well if it's Laserdiscs I keep going back to watching over and over:

Seal [WML5-7018] - only way to get the acoustic version of my favorite song from him "Wild." Plus, this Japanese release is in Dolby Surround (US release is in stereo.)

Viz' Ranma 1/2 releases Desperately Seeking Shampoo [LVD9528] and Like Water for Ranma [LVD9544] - they look better than Viz' DVD release to me, and they're in CAV. Only wish they would have used the proper translation for the closed captions for the first release, rather than just the dub captions. They did use their subtitle translation for the captions of the second release. Would have been really cool if they finished releasing the OAVs on LD, but it wasn't meant to be.

Beauty and the Beast [1325 AS] - mostly because it's the way it looked back in 1991, and I love showing my friends who have the movie on DVD what they're missing out on (LD is letterboxed 1.66:1, subsequent DVD and Blu-rays are at 1.85:1 and 1.78:1.)

Suspiria: Spectral Collection [SHLY-113] - really nice transfer of one of my favorite horror movies. Even though I have the Anchor Bay 3-disc Limited Edition DVD, I still find myself going back to this release to watch the movie.