OMG!!!! You have to get Space Thing for the commentary. It starts with Dave Friedman, the director saying that Space Thing was the worst movie he had ever done. The golden moment is when Friedman starts on a new thread of conversation, and Mike Vraney of Something Weird tells him that he has to stop because they've hit the end of the movie.

I'm really, really fond of the C.H.U.D. commentary. Seriously.

How do you make one the greatest comedies of all time even better? Listen to the This Is Spinal Tap commentary. Guest, Shearer and McKean do it in character and it's absolutely superb. It really goes to show what great ad libbers the three of them are.

While watching Get Carter, with the commentary on, Caine points out in the bar scene (when he arrives in New Castle) there is an old guy who raises a glass to his mouth which shows he has an extra finger.

I always liked Lloyd Kaufman's commentary tracks. Regardless of what you may think of Troma films, they are infinitely more palpable to the detractors with Kaufman's voice laid over the visuals.

Total Recall - Arnie and Verhoeven double act. Very amusing.

Gaspar Noe's commentary for Irreversible is very insightful. He actually pointed out stuff that had completely passed me by even though I've seen the film about 5 times!

Shaun of the Dead commentaries are all great as are the Hot Fuzz ones: spoilt for choice if anything with these.

Which releasing of Irreversible has a Noe commentary? I have the unrrated Lion's Gate release, but has fuck-all for extras.

This

Well worth getting hold of.

The Day the Earth Stood Still (1951) is pretty interesting, it's been around for ages as it was recorded for the laserdisc, and it's between director Robert Wise and his friend/director Nicholas Meyer who is very knowledgable on the film we're watching and often, politely, corrects Wise's anecdotes. It's mostly very interesting to hear the directors of Star Trek I and II talking about old sci-fi films!

As soon as I saw this thread title I thought of the Carpenter/Russell pairing on practically anything, and TRON also, so it's nice to see both of them get mentioned!

I recently picked up Hardware but I haven't checked out the commentary for that yet. Might give it a shot tonight.. I remember liking the Ghostbusters commentary, though I was probably bias since it was the first DVD I ever bought and these things still had that "Ooh, new!" factor..

After posting this question over a year ago, four of us finally got around to our Commentaryfest this weekend. We ended up watching:

Conan the Barbarian: A 'read-along book' retelling of the on screen events by Arnie.
Clerks (10th Anniv First Cut Commentary): A few funny anecdotes.
Evil Dead II Collector's Ed: Bruce Campbell with a few film-making anecdotes and witterings.
Aliens: Definitive Ed: easily the best commentary of four, packed full with detail.

Overall, not very successful. We spent most of the time wishing we had just re-watched the movies!

One that hasn't been mentioned so far is "UHF". The commentary with Weird Al is packed with information. Al even gives the street addresses of lots of the filming locations.

Mark Kermode and William Peter Blatty - The Ninth Configuration.

Any commentary featuring Kim Newman and Stephen Jones.