That's actually an easy question for me to answer. While I had (and still have) all of the Aurora monster model kits, they really didn't qualify as toys you could play with. Action figures weren't the standard boy's toy that they are today, and the many rubber "jigglers" I had, were really too small to pose a threat to my 12" G.I. Joe battalion, so they didn't get much play unless I was pitting them against each other.
The monster toys that I played with the most, and remember most fondly, are these:
Plastic dinosaurs, army men, knights, cowboys, indians, astronauts, etc., were my go to toy for epic battles in the sandbox. My plastic dinosaurs mainly consisted of those, then, realistic versions produced by the Marx Toy Company, but somewhere along the line one of my grandparents handed me a plastic bag of assorted dinosaurs from a dime store. These consisted of various small plastic dinosaurs in primary bright colors, and then these oddities which were painted with care and detail. As a 6-7 year old I didn't know what the hell these were. They certainly weren't dinosaurs, and had no business being packaged with them. Still I was really attracted to them, and found a great use for them, though surprisingly it wasn't as kaiju.
No, these were the crew of a spaceship commanded by two identical, yet differently colored plastic soldiers who could also transform into megatheriums (a story telling necessity, when one of these main character soldiers was lost for weeks somewhere deep under the sand). These alien crew members were all good guys and had distinct personalities, crew positions, and special powers. I think I was guided mostly by The Guardians of the Galaxy and cartoon shows like The Herculoids. The large grey alien with the outstretched arms was my version of Igoo. The green spiky guy on the end was the helmsman. The red dragon looking guy with the fire snorting out of his nose was for some reason one of my favorites and he got a big roll in every story. I think his entire body was fire, too, like the human torch. He was also the smartest member of the crew. The blue four-legged creature with the horn on it's nose was the equivalent of Dino on the Flintstones. The two upright creatures that are identical except for size and color, were parent and child, gentle and could burrow through the earth. The other four-legged creature in front of Igoo, could also burrow and was something like an armored attack dog. I have no idea what I did with the scorpion like creature, and I think that weird tiny green guy (whose origin point I couldn't tell you) was some weird mutant creature that they would encounter from time to time on different planets, where acorn caps still attached to twigs were ground plants which could suck out your brains.
In addition to the above, the crew also included a female kangaroo and a monkey named Cheeta. The central antagonist was a time traveling cowboy named James Garner, clearly patterned on The Master from Doctor Who.
An interesting fact about my childhood. From the earliest time I always played things as a long serialized narrative, with episodes picking up from where I left off the day before. Like I said before, after temporarily losing my main character, I had to deal with his absence, and for whatever reason he was transformed into a talking giant ground sloth until a "cure" (ie; the plastic soldier's recovery from wherever he was buried) could be found. I also recall that this long storyline which lasted for years, culminated in a showdown with James Garner on a planet that was slowly being devoured by its sun. I think everyone might have perished, but I distinctly remember that James Garner was incinerated by the sun once it reached him, even though he merely felt warm when the edge of the sun was just a few feet away from him.