Lets see...
There was USS Bravo, a mod that was supposed to be like USS Darkstar but with brighter maps. I made a dorm room, a few corridors, and a bridge where the plot development would happen, complete with a fully-functional elevator. That lasted for a day or two before I dropped it and deleted the source files outright to save disk space.
After that, I switched to a mod with a name I can't remember that was going to be set during the Seven Hour War, but in a universe where Half-Life the game existed as well as Half-Life the events, so the player character had a big crate with a fully-functional HEV suit replica and a poster of Alyx in their apartment. They would then attempt to use the elevator in their apartment complex, only for it to literally break apart and drop them into the sewers, which they would have to navigate to get into the basement of the office building across the street. That's where I ran out of ideas and dropped the project, though IIRC a partial backup of that (single map) mod made it into Castle Disposed.
Once I dropped that, I started a brand new mod that I called USS Bravo, originally based off of USS Darkstar. If anything I got even less far than my first attempt, but the maps were much better looking and featured Otis as well as Barney as guards (IIRC I just grabbed the model from Blue Shift and plopped it on a monster_generic, as this was before I started using Spirit of Half-Life)
Speaking of Spirit, I downloaded some unofficial mongrel build of Spirit that called itself 1.7 and had features that the base mod didn't such as a suppressor for the pistol and a system that changed what arms the player had based on whether or not the had the HEV suit (neither of these was configurable or could be disabled) and tried to make a prison breakout mod that I think was set after the Black Mesa incident, like you had been kidnapped by the Black Ops guys? All I really remember from that is that I had a security camera you could use.
Then, I started yet another mod, this time set directly during the black mesa incident, where you played as a janitor (Unbeknownst to me that had apparently been done). This is another one that didn't make it past 1 or 2 maps because I had done literally zero planning, but, like the 7-hour war mod, a partial version of the first map ended up in Castle Disposed, albeit with the Blue Shift and Opposing Force BMRF propaganda posters I used replaced with somewhat tasteless demotivational posters by Tetsu0.
The only notable HL mod I canceled aside from all that garbage was Colony 42, a mod that was just, once again, USS Darkstar with more lights, but this time on a space station instead of a ship, but which still somehow saw the light of day and was apparently finished enough that Urby wants to remake it, though I did at one point briefly consider also making a full campaign addon or mod for They Hunger where you played as a person who was not at all having a good recovery in a convalescent home.