Hmmm...that's a hard question, I have too many favourites to choose but here goes...
Baby (or in-training but I prefer to say baby): Calumon
Rookies: Gomamon, Patamon, Gazimon, Renamon, Impmon, Gaomon and Kudamon
Champion: Garurumon, Tailmon, Kyubimon, Blacktailmon, Tobucatmon, Blackgarurumon, Youkomon and Sangloupmon
Ultimate: Qilinmon and Mihiramon
Mega: Banchouleomon, Sleipmon, Lilithmon, Sakuyamon, Alforceveedramon and Beelzemon
Armour: Pegasusmon, Goatmon and Raidramon
I have to choose one favourite digimon that would be Kudamon because not only I adore ferret-looking digimon like him (blame savers' design), I also do not mind the original pipe fox design as well as the evolutions are awesome.