I believe on my first playthrough as a kid, I had Pokemon Crystal. The Pokemon I caught I believe was Feraligatr, Onix, Haunter, Growlithe, Electrode, Scyther, Sudowoodo, Skarmory, a red shiny Golbat, a red shiny Gyarados, Mantine, Donphan, Poliwhirl, Quagsire and Umbreon.
I can't really remember which Pokemon I focused on except for Feraligatr but I recall catching a lot of Pokemon that couldn't evolve yet because I didn't have a trade link cable or that evolutionary stones weren't available at the time. Pokemon Crystal Version was my first Pokemon Main Series game actually so I was probably like six or seven at the time and I thought Steel Type were just the coolest. Funny thing is I never actually beat the game at the time, I was stuck after the 8th Gym Leader having no clue what to do afterwards lol, not realizing there was an entire new region to explore next to Johto. Although Feraligatr was definitely a memorable Pokemon, I can still remember his colorful evolution animation. Scyther was a Pokemon hard to catch only to find out I couldn't evolve it to Scizor lol because of no trade cable. Sudowoodo was a fun surprise and Skarmory was quite unexpected, finding it after the 8th gym. However a really unexpected counter was that I found a red shiny Golbat in Mt. Mortar.