Chose based on a mix of aesthetics and battle experience. Shifts somewhat too, based on any given day. Probably rated Aegislash higher before.
Finds it interesting how much weight battle experience carries. Spans from never used to star of an initial playthrough. Elevated some, like Staraptor . Harmed others, like Serperior . Imagines rankings changing after playing with all of them under equal conditions.
Hoo boy, picking any one favorite is hard to do since I tend to appreciate all of the pokemon designs for one reason or another (save for one exception but I digress) but if you exclude any legendaries or starters/popular 'mons, and in no particular order, I'd have to go with:
1. Love the sleek design and I had a lot of fun using her as a glass cannon in my casual runs!
2. Favorite Gen 1 Eeveelution and a good bulky water type all around (Ok so maybe one popular 'mon)
3. I'm a sucker for cute Pokemon and Alcremie pulls that off flawlessly (and being dessert-themed without making the design look kind of wonky to boot!)
4. I love reading up on history and Claydol captures the fun mystery of ancient times perfectly, not to mention being really fun to use
5. / It's a toss-up between these two as I used both pretty heavily back during ORAS on rain teams, love the designs as well!
6. This pokemon is near and dear to my heart as the very first pokemon I had to hunt for all the way back during RBY, and I proudly used her in Stadium to beat down the Gym leader castle
7. Out of the bevy of Gen 1 Normal/Flying Pokemon Dodrio has always been my favorite, fun design and just as much fun of a playstyle too
8. // Yet another tie, as I love these guys for much the same reason, their designs giving me flashbacks to Godzilla vs Hedorah and just being good bulky Poison-types all round helps!
9. As a kid who grew up with Leafgreen and was too impatient to search for I grew to appreciate having a bulkier 'mon to help make up for my admittedly sloppy battling, and that movepool was just great
10. I have no real explanation for this little guy, save for it's just so cool
I'll drop my top 10.
1. Love this guy. Really cool design, and fun to use both in game and competitively.
2. Before I was Rex, I was tyranitarusrex248.
3. Used him in game during my first Sun playthrough and fell in love. Haters gonna hate.
4. I love these little dudes. It was love at first sight.
5. An MVP of my very first Nuzlocke.
6. I can't really explain my love for this weirdo.
7. My first starter, and still my favorite.
8. Another party member from my first Sun playthrough. Love the scarf, and one of my favorite shinies.
9. Fan favorite for a reason. ORAS did him dirty, not providing a Mega.
10. I couldn't believe this things evolution method. Just so gimmicky but high key fun.