When I played, I was determined to beat the Elite Four using a team of my favorites - most were caught in the beginning routes and are Pokemon that a lot of people would consider useless. They were all around level 60, and were:
Typhlosion (Not bad at all, traded from my Crystal game)
Pidgeot (As other people have mentioned, not just your average Flyer)
Quagsire (Earthquake and Ice Punce were utilized great on this guy, traded from my Crystal game)
Rattata (Suprisingly, Super Fang combined with his speed made this guy deadly)
Scyther (Again, speed combined with some choice TMs were utilized)
Butterfree (Sleep Powder and Psychic made Butterfree one of the Pokemon I used most, actually)
I actually beat them!