On my Diamond, I'm proud of 3 pokemon.
1. Naughty Luxray. Can easily pull me out of tough spots against physical powerhouses due to its intimidate ability.
2. Brave Lucario. I love the high offensive stats. Its great with its earthquake and focus blast.
3. (Forgot it's nature) Shiny Scizor. For something I just got not too long ago, I'm impressed.
On FireRed, only 2...
1. Mild Charizard. Its very rare that I'm satisfied with a starter pokemon. Its saved me on a few occasions and can hold its own against quite a few legends.
2. Brave Jolteon. This pokemon I feel is so much more impressive than even my Luxray. Despite than it has a considerably lower attack stat than Luxray and doesn't have Luxray's intimidate. Thunder is kind of inaccurate. All I'm saying is I hardly see the move fail. I love my Jolteon.