The only event Pokémon I got in Gen3 was Jirachi because of the Colosseum Bonus Disc.
I also had the Eon Ticket e-Reader card from Nintendo Power, which I think counts as an event, but only gives you Latios or Latias.
>>19356327How do you get the Mew or Deoxys events in Gen3 in the US?
Another event I never could find was the Ho-oh/Lugia island, but they're both obtainable in Gamecube games anyway.
The first time I ever got a legit Mew was in Ranch
My first Deoxys was a Gen4 GameStop event