Adventure setting, number of players, demographics, the WHOLE thing. What's the best crew you've ever had, and what is the best combination of classes you've seen?

Personally, I remember a campaign where everyone was a half-caster or higher.  Hexblade, Eldritch Knight, Twilight cleric, and a Shepard Druid in a low level campaign. Goblins could simply not exist for long within casting range. I was still learning the ropes then, so I used a written adventure (LMOP). Still was fun   

Four players, summer after we graduated high school. The campaign, which had around ten sessions and went to fourth level, cast the characters as a crew of thieves pulling off Ocean’s-like heists in the Renaissance-meets-fantasy setting of Verillion, the City of Silks. One guy played a goblin barbarian named Nehemiah “Neh” Greenskin, a fiery little jerk with a heart of gold who remained the de facto leader despite abandoning his friends multiple times. He was my favorite character ever to DM for, with unpredictability like watching Loki in a Marvel movie. Another guy went through four colorful characters, as three of them died in a single adventure (we did not pull punches in that game). He was a great sport. Our quietest and least experienced player was a halfling trickery cleric named Faux, who came up with the biggest clutch move I’ve ever seen when she, after hanging in back the whole session, absolutely wrecked a boss fight with Pass Without Trace. And the last guy...well, he had the most unceremonious and hilarious death ever when his bard, Johannes, was caught by the lord he stole from, and when asked “what do you have to say for yourself?” just accepted his death. I felt bad, but I also couldn’t stop laughing. :-/ The surviving characters ended up skipping town in the last session after being caught between two rival crime bosses, and they now live happily in a small town, of which Neh is the mayor.

I ran a really fun one that I called guardians of time. I sadly had to end it because I did not have enough time availabilities, but here's the rundown:

I ran it over play by post on the dnd beyond forums (recruitment thread, game thread if you want to give them a read). the party had a knowledge cleric, a a twilight cleric, an evocation wizard, a chronurgy wizard, an arcane trickster rogue, and an arcane archer fighter. the group role played really well, and, although we never got to much of the actual story, I had SO much fun running it! (mostly because my group was amazing. thanks if any of you are reading this). the basic plot was that mysterious artifacts called time shards that have the power of time started disappearing from there hidden location, seemingly being stolen. the players were tasked with recovering the artifacts by an emperor. however, each one was only accessible at a certain point in time. luckily for the party and the plot, one of them was accessible at the start of the campaign. had the campaign have lasted, the party would have found its hiding place eventually, defeated the guard, a great storm elemental that gave the ocean its name, and found the first time shard. in the prosses, they would have discovered much lore and history about the world, which would have made previous, seemingly inexplicable even make sense. they could have used the time shard to travel through time, finding all the time shards while learning more very useful lore about the world, eventually ending in a climatic battle with a time wizard who was the one stealing the artifacts.

I ran a homebrew module I titled "The Forge" for a group I run with a local game shop.  Story overview was 1000 years prior, an underground civilization had been experimenting with interplanar travel to the far realm, and unwillingly summoned a powerful entity which wreaked destruction, only being stopped by being sealed into the inner reaches of the city by a powerful artifact called simply "the key" The party (in the present), sent to recover the heirlooms of a wealthy merchant from his childhood home that had been buried in a sandstorm, uncovered a secret:  the merchants family had been entrusted to guard the Key.  By bringing the Key out of its hiding place, they attracted the attention of the entity (a beholder who augmented its body and became a death tyrant while plotting his escape), who began trying to recover the key to release itself from its prison.

The party researched the Key and its history (in what was my favorite session, they ran a simultaneous mission;  half of the party attending a fancy party to glean information from a group of nobles, the other half infiltrating their castle to search for clues/evidence in the castle archives, which were closed to the public due to one of the nobles attempting to conceal evidence of massive graft and fraud, they wound up kidnapping the guilty noble (prior to knowing he was guilty, lol) at the end because he discovered them.  They also had to seek help from a powerful Djinni who created the Key, while fending off attacks from construct armies remote controlled by the entity, before descending into the fallen city to face the entity itself before its remote controlled armies could threaten the world.  The back half of the campaign was the city itself, a mega-dungeon that incorporated elements from the SCP universe as monsters that had been summoned and imprisoned in the city.

Levels were 8 to 12, with a main party of 5 including a Tiefling Whispers Bard/ Hexblade Warlock, Goblin Battlesmith Artificer, Dwarven Hunter Ranger, Elvish Evocation Wizard, and Elvish Moon Druid.  

I created a oneshot detailing the original invasion of the entity, and the effort to seal it into the city, for level 8 characters as well.  the first time I ran it, the group was successful, but only one survived (about what I was expecting)