I have a bunch of favorite Pokemon, so I will name each one that I can think of right now. Infernape, Typhlosion, Emboar, Beedrill, Giratina, Yanmega, Raikou, Registeel, Umbreon, and Gallade. Each one is really strong, or at least with the way I trained them.
1. Ferrothorn: In my battling life, I rarely never used ferrothorn. His Walling and defensive capabilities have played many pivotal parts in my battles, especially stealth rock set ups and throwing leech seeds to wall my opponents
2. Heatran: Also, another pokemon to help in walling my opponents. Since my Ferrothorn is weak to fire, Heatran can help eat up any fire attacks with its ability, making heatran and ferrothorn a great combo.
3. Garchomp: This is my strongest sweeper in my team. With his great attack and speed, Garchomp has been my most efficient attacker in my team, pulling off late game sweeps.
My top 3 non-competitive pokemon:
1. Gardevoir: DON'T ASK >:P
2. Spheal: Spheal has always been one of my faves in terms of cuteness... And more importantly, he's a ball! XP
3. Togekiss: I got mixed feelings for this one... I really like it in terms of its design and stuff but at the same time, in battling, I distaste it for its underhanded parahaxing trick... And I get pissed immediately when I see my opponents carrying it.
My Sinnoh starter. Even though Empoleon was far from the best starter of its gen, it was my favorite simply because it looked awesome. The steel/water typing really isn't that great though.
4. Tyranitar
My favorite pseudo legend. Tyranitar also had an awesome design, and a not-so-great typing. Despite that, Tyranitar is great. After getting one late game in gen 2, I hardly ever would take it off my team.
3. Pigeot
Pigeot has always been the sidekick to my starter in the early gens. It was the first pokemon I actually captured and it stayed on my team for a majority of the game. It frequently found itself as the second highest leveled pokemon on my team, following my starter. It also is a fly slave, which is nice.
2. Weavile
Weavile's speed and power are great competitively. Like everything else on this list, its design is great. I like the personality they put into it too, it fits my name.
1. Typhlosion
Might have mentioned this a few times before, but whatever. Typhlosion was the first pokemon I ever had in game. It is also the first legit level 100 I had. Typhlosion never left my team in gen 2, and it was awesome. It isn't too bad competitively either, when played smartly.