Treecko, Grovyle, and Sceptile.
When Pokemon Ruby/Sapphire came out in the U.S, one of my best friends, (who moved away...) Brandon, had a copy of the Sapphire version. I asked him which starter he chose, and he said Treecko, because it's cool.
So when I eventauly got my copy of the Ruby version, I chose Treecko, as my starter. I found that it was much cooler than the discription Brandon made, and it learned very powerful moves. When it evolved into Grovyle, and then a Sceptile, it just got even more powerful and much more cool.
When the Pokemon Advanced anime came out later, I noticed that Ash's Treecko had a really distinct personality. He was quite a loner, perfering to sit alone rather than eat or hang out with the other pokemon. he also had a rebellious attitude, crossing his arms in that cool fashion, being the only pokemon refusing to dance in Gotta Dance, only to ironicly become the best dancer at the end. I fell in love with the three pokemon.
These awesome lizards are the reason why I love the Advanced generation more than the others.