You always make the best topics, Brian!
My main lines were Star Wars, Masters of the Universe, and Transformers, and I supplemented with figures from other lines as I saw fit. I have plenty of memories, though they are fragmented like yours in some places...
Inhumanoids--I had one of the trees...Redwood? I loved the show so much, and really wished the toy line matched up better. One of my friends had Despayre (the big skeletal bad guy with Starscream/Cobra Commander's voice on the show) and he was a lot of fun to throw into Star Wars or GI Joe battles
MASK--I had the Raven Corvette. I remember using the driver as a kid when mixing him with the Star Wars guys.
Dino Riders--I had the Triceratops. I wanted to be all in with the line, but I wasn't happy with the dinosaur's posabaility and I was getting older.
GI Joe--I had to have Destro. He menaced Luke and Han many a day. Later, as Star Wars died, I started buying more random Joes and Cobras. My friends and I would take them apart and build figures of the superheroes we would make up, so it never was a GI Joe thing.
GoBots--Turbo and Scooter joined the Autobots. I mean, Scooter was such a ridiculous character, I had to own him!
BlackStar--I had one of them but I couldn't tell you which one, I only got it for the little demon pack-in figure:

<---this guy attacked everybody!
Sectaurs: Whoever it was that came with the little biting bug. I think he was the equivalent of Man-At-Arms...
Visionaries: Arzon, the Eagle totem. I wanted to love these but the media made them more exciting than the reality.
Wheeled Warriors: the bad guy with the circular saw on the roof.
I have to put in a special mention of a whole line I played with as a "one-off" too. On vacation one summer my younger brother and I found a new line of toys called "Sky Commanders" all clearanced out at KayBee toys, and over the course of a few weeks collected everything we could cajole our parents into buying--they were cheap so it wound up being a lot. It was fun with lots of ziplines and creative play, but its cartoon got lost on USA's Cartoon Express and it died quick. That's one I would go back and recollect for the nostalgia.