@Iroh do you have a preference toward any kind of type?
I know several off hand, you could have agumon as a rookie and go up the tyrannomon line (tyrannomon, metaltyrannomon, rusttyrannomon)
i mentioned the veemon line, veedramon, aeroveedramon, ulforceveedramon
one i'm not quite happy with is goburimon, ogremon, digitamamon, titamon, i really like goburimon/ogremon and titamon but i'm not happy with digitamamon as the ultimate... it's just so out of place with the other forms
let's see... you could do tentomon up the kuwagamon line, kuwagamon, okuwamon, grankuwagamon (or grandiskuwagamon, whichever you prefer, grandis is more humanoid)
there's the wonderfully awesome dorumon line, dorugamon, dorugreymon, dorugoramon
those are all i can think of off hand without looking stuff up but its a lot xD
@Kurogane86 that's actually pretty easy Tapirmon (i prefer that version of his name, you don't have to use it) goes to boarmon, then mammothmon, then skullmammothmon, check them and see if you like em (i suggest using digimon.wikia.com over wikimon)