First off, let me say that the show NEVER impacted my love for these figures, it was toys first and foremost for me. Pretty much everything Takara did had "awesome" on it, and everything Hasbro designed was shitty.
Astrotrain - pretty much couldn't not like this guy, and the purple/black version, not the accurately-colored one.
Blitzwing - I actually only have a knockoff of this one, but it's a really nifty execution. I mean, I have Broadside as well but he sucks!
Blurr - I dug the alt mode really more than anything.
Bruticus - I prefer the scramble-city style gestalts, and this one just seemed to make the most sense at the time. I liked 'em all separately. The funny thing is, Onslaught is my least-favorite of the group merely because he's the least interesting vehicle and bot.
Bumblebee - may have been influenced by the show, but I had a thing for VW Beetles and Penny Racers at the time.
Buzzsaw - I didn't care about Laserbeak vs Buzzsaw, Buzzsaw came with Soundwave so I didn't need Laserbeak.
Cosmos - I liked that this existed at all.
Fortress Maximus - I don't even remember how I ended up with this one, but I dug the base mode.
Frenzy & Rumble - this may have been more about the show, but I liked the cassette to bot thing on its own as well.
Hot Rod - this was about alt mode, but I also found the bot mode satisfying at the time.
Huffer - I just dug this one, not sure why.
Mirage - I liked the way he transformed.
Omega Supreme - I had him as a kid and didn't really like the legoforming, but did like the base mode and rocket turning into a big thing.
Omnibots - I liked the concept of alt modes that transformed too.
Optimus Prime - natch. I think I actually liked him more for his gimmick trailer than himself, as I had already bought Ultra Magnus who to me was the same dude but could combine.
Overdrive - my favorite of the Omnibots, had the best of every mode, and it flew!
Powermaster Optimus Prime - I was a kid and it did cool stuff, what can I say? I even liked the base mode.
Ravage - not my favorite cassettebot, but a pretty neat concept.
Seaspray - I have a thing for hovercrafts.
Shockwave - I really liked the gun mode, and the bot mode was ok too so it was a win.
Soundwave - probably the ultimate Transformer, even his friggin' batteries transformed! And he had decent articulation at a time when they were bricks usually.
Tracks - a kickass alt mode and basically an Omnibot with the modified alt mode.
Ultra Magnus - I really liked this figure, probably a little more than Optimus at the time even, because he merged with his trailer and his trailer could hold other guys.
Wheeljack - mainly because of the alt mode.
Whirl - I think I was intrigued by both his modes, but never actually owned him.