Show and tell! Your 12 oldest Pokemon
Maybe you kept your starter. Maybe they have sentimental value. Maybe you have maxed them out and they're still usable. For whatever reason, you've kept them. Show us your oldest 12 Pokémon!
I keep the hitmonchan because it was the first high-IV Pokemon I got. Buterfree, Beedrill,and Nidoking because they are the highest IVs of their species that I have caught to this day.
The vaps, eggy, nidoqueen, jolteon and lapras were the backbone of my attack team back in the day and I still use some of them sometimes. I keep the flareon cuz it's legacy and I don't know why I keep the Arcanine but I probably have a good reason.

Answers
The Mimes and Tauros, only b/c they're regionals I likely won't catch another of for some time. Rhydon, Charizard, Nidoqueen, and Ninetales are the highest IV I have of each. Golem, Magneton, Exeggutor, Vileplume, and Victreebel - keeping them for no particular reason. I'll get around to transferring maybe one or two of them for a quest maybe.
I catched all of these between July 20th and August 21st, I've started to play at July 13th
The Slowbro and Poliwrath were 2 of my favorite defenders during 1st Gen (oh good old Bubble...)
Dragonite, Gengar and Weezing carry Legacy moves with them (Dragon Claw, Shadowclaw and Acid)
Scizor (93%) and Victreebell (100%) are maxed, the first is one of my favorite Pokemon, the second was/is pretty useful despite low bulk because of Leaf Blade
Dragonair was my first rare catch (even before my first Dratini) and also my first (long time) buddy
I want to max my Rhydon, when Gen 4 arrives, I have another 98% and a 96% at the same level, but this one is by far the oldest of them
I always wanted to max my 98% Vaporeon, but i always had something better to push - even back then - and now... the list is bigger than ever... one day, Calypso, one day.
Raichu 98% - best IV Raichu I got to date, I keep a living Pokedex, that one is King of the non event Raichu
Arcanine, a mediocre IV catch I pushed just because I love this 'mon. Well I'm still seeking for a 93%+ one that I can max, just because
Did anyone really read this? (without thinking about suicide or mass destruction?)
Hitmonlee was my first 10k hatch and Magmar my first pokemon above 1000 cp. I was sick of having low CP pokemon so i found a high cp Eevee (I had no idea about IV's back then), evolved it and powered it up to 1711 cp. I had the highest cp mon of all my friends. Turned out to be an Vaporeon with 15-13-12 IV's (ADS) and powered it up from there. Boy I was happy when i checked her IV's.
Most of mine are just "strongest of that species that I have", with a few exceptions. Origin is my starter, and will be a Hydro Cannon Blastoise when that drops. Pika was my first Pikachu, and Bowyer is my 9x% Confusion Exeggutor. Snorlax and Lapras are just there because they were my first for each.