[Klauser]

DS9 was the product that really changed stuff for us here. It was the first product you could buy a starter and some 5 boosters (either at a tournament or just in a shop) and go home and build a themed deck that actually worked that was almost always a good deck and one or two affiliations and really playable.

It was a design marvel. It was a semi-random starter with a trifecta of Fed, Baj and Car with some NA sprinkled in for good measure and need. The cards were set up in a circle so that each affiliation got a third of it and a treaty between each affiliation if you got some sort of flow over to another affiliation (the best starter was always the mixed Fed/Car because of the seedable Klaestron Outpost). This setup made the card sorting for the factory easier as well as more or less promising a playable deck in each starter (some few misses could be found but with the help of a couple of boosters and extra treaties to borrow during a sealed event would alleviate this problem). ...

While DS9 was not a big hit (*) in my area when it came out, I have to admit your point about a starter deck and 5 expansion packs is spot on. I was a local ambassador during that era and over several tournaments I cannot remember a time building a workable deck was a problem.

* - Side Note: The whole "Nors had to have sites to report" concept did not go over well here.

[sexecutioner]

Difficult one. I don't blame others for seperating their answers to Decipher and CC

Decipher - Blaze of Glory: Capturing got a lot more fun. Locutus Borg Cube. And of course, Tactics made Ship battles more 'Trek sense' and exciting.

CC - As much as I love The Next Generation, Resistance is Futile gave me incentive to assimilate my opponents ships, paving the way for my 'pure assimilation' decks that could finally have a chance of achieving full wins.

[Iron Prime]

I don't know if I could pick just one? So many great answers in this thread so far.

I will always have a soft spot for Premiere, FC, and BoG. But at the end of the day I really think that TNG might be the winner as it guided so many PAQ players back into the game...

[Data's Socks]

The cards were set up in a circle so that each affiliation got a third of it and a treaty between each affiliation if you got some sort of flow over to another affiliation (the best starter was always the mixed Fed/Car because of the seedable Klaestron Outpost).

Ah, so that's how it was. That is really cool.

Deep Space Nine is a set I'd love to crack open more packs of. Strangely enough I don't find most of the rares to be particularly exciting; maybe they just don't stand out that much relative to the commons and uncommons. But the overall presentation is so good. It felt like the game was finding its stride.

I always thought it formed an A and a U...

Aye, it's the gift that keeps on giving!

[Borg King]

• First Contact -- COMPLETELY changed the game and largely for the better. From relaxing the 60-card deck size limit (causing the most impactful changes in deck design philosophy in the game's history), to turning the metagame upside down (Mirror Image, Intermix Ratio, TLMBDH were the first bullets with real teeth), to introducing new mechanics (downloading, probing, the Borg!)
  
  I remember reading over the First Contact rules sheet when the expansion first came out, and my jaw dropping further and further with each paragraph. The expansion literally rebooted the game.
• Official Tournament Sealed Deck -- Card-for-card the highest-quality product Decipher ever produced, and a masterpiece of design. In just 20 cards, Decipher ensured that virtually any collection of Premiere/AU cards would be playable (even including the Tama in case you stumbled upon a Particle Scattering Field!) and balanced (Spacedoor and Open Diplomatic Relations preventing a stray Red Alert! or The Devil from ruining your day). The cards are equally useful in Constructed, even more than two decades later, and still range from playable to ubiquitous. Only one of them had any real balance issues (Space-Time Portal), and it was easy to fix.
  
  In terms of quality, balance, and economy, no other 1E product comes close.
• Blaze of Glory -- A good expansion, but more so than the specific product this era was my favorite time to be playing the game. Without straining too hard, you could make a competitive deck with any affiliation, and the game pace was perfect (none of the monotonous "Sito Jaxa reporting for duty, now your turn" Premiere days, and crazy 30-minute first turn Hexany wins were still far away)

100% all this. Glory days of the game with DS9 also opening up a lot of doors for gameplay.

The CC stuff I'm still slowly wading through, but The Cage is probably my favorite as there is a lot of fun stuff in there!

[Tim]

Back in the day, the funnest PACK to open was Mirror, Mirror: Better chance of pulling a lead character (even if mirror version), other rares all seemed good and it didn't have any filler card types.

[Shepard]

I'm late to this party, but First Contact will probably always be the set I have the most nostalgia for. I loved the movie when it came out (it's still probably my favourite of all the Trek movies), and it was one of the more revolutionary sets in the early game (downloads blew my mind when OTSD and FC first hit, and of course the introduction of the Borg and time travel were just brilliant). It's also the first set I ever really remembered being blown away by the overall art - Fajo had some cool stuff with the image bleeds into the margins and such, but some of the cards in FC were just pretty (Patrol Neutral Zone is still one of my favourite images on a card).

In the CC era, I've loved almost all of the sets for one reason or another, but yeah, like many others here TNG is also the one that I think the most fondly of. I remember being a lurker on the site and the forums for stuff like Straight and Steady and Shades of Grey, and while I was excited at the new content and the fleshing out of various affiliations and strategies, the double whammy of TNG and the introduction of OTF seemed to me even at the time very inspired and savvy. Those two events probably are to this day the most defining moments of the CC era, imo.

[Mr.Sloan]

Deep Space Nine.

It introduced a nice play enrivonment with 2 new affiliation. Play 2 draw 2 time. good times.

[Dunnagh]

wow wow wow... so many good sets!

For me, its gotta be
Premiere

We had so much fun with it - and still have. I remember being in the USA for the only time in my life and visiting a comic book store there to actually BUY a couple of rares. I got 5 Wormhole Negotiations but no Main character except Tasha. So I bought Deanna and Worf and was the happiest guy ever. The main set is the reason why everyone here is actually here. Yes, it was flawed in some ways but the basic idea - storytelling in a ccg - was awesome (and only Middle Earth CCG tried something like this).

The reason why we are STILLhere though is a different set - and I´d also say Deep Space Nine It introduced us to many new concepts that sped up the game (downloads were in FC though) and gave us much more than "play a card, draw a card".

[Ensign Q]

since I only played Premiere and AU back then its hard for me to evaluate the sets. I like the flavor of AU, but the powerlevel is horrible. Future Enterprise though!
First Contact definitely looked the most interesting but at that point I had nobody to play with. Also thats when I lost track of the rules anyway. Different Quads, the Borg, Wtf.

Today I havent played enough to really evaluate the sets, but from the custom sets I like Shades of Grey the most, because it blows fresh wind into old dilemma and feels overall the best designed set. Only flaw is the not deeply enough explored Hotel Royale episode.