I remmember cracking open tons of missions from either ST:R and BP, but I've never... EVER seen something as sickling as alphabetically ordered sexps.
I was not expecting to see something like that, and so I nominate Goober.
Eh? When did I alphabetize sexps?
I remember being very impressed with how extensively the Beyond the Red Line campaign used branching, particularly the Scar mission where the mission accommodated everything from your performance in the prior mission to the player explicitly cheating. (Which, upon rereading Karajorma's post, I see that he's already linked to.) And that's on top of the regular FREDding to make a very entertaining and playable mission just at face value. And this is from someone who hasn't seen the reimagined BSG.
The Blue Planet missions are also extremely technically well made, though I've never cracked one open to take a look at it. I imagine I'd find pages and pages of sexps, many with when-argument. I still need to play JAD 2.22 and Wings of Dawn too.
A special mention has to go to Windmills, which is entirely in a class of its own FREDding-wise. I didn't particularly like the campaign, but it was a technical tour-de-force.
For my own missions, I'm particularly pleased with He Who Rides the Tiger and Blood of the Innocents in ST:R, both of which involved some heavy-duty creative sexping to get things to play out exactly as I wanted to. He Who Rides the Tiger had the additional challenge of trying to stuff everything into the retail sexp limit. But I think the most technically complex mission I've written (that's released, anyway) is I Has A Limit, the penultimate mission of DEM 1.5. It uses the camera sexps, variables and when-argument, stupid AI tricks, and cutscene hacks, and it even screws with the HUD. Furthermore, it uses a cloaked AI ship to increase the resolution of the sexp event delays, as the
mission-time-msecs sexp didn't exist yet.
I also have to mention Bem Cavalgar, which took the proof of concept I published way back in the day as FreeSpaceLancer and finally made a playable campaign out of it. A pretty good campaign, too.
I think the missions I'm most looking forward to playing, though, are the ones in Between the Ashes. The demo missions are
extremely dense with plot and content, very fun to play (once I actually understood what I was supposed to be doing) and technically top-notch. The actual campaign missions should be even better.