From each Gen...
Gen 1 - Snorlax (Blocking your path!)
Gen 2 - Donphan (He's a tank, and elephants are pretty cool)
Gen 3 - Gardevoir (Was always fun to catch and raise a Ralts)
Gen 4 - Electivire (Used him in White 2, where I fell in love with him)
Gen 5 - Darmanitan (Just look at him, dude's a boss)
Gen 6 - To be determined