This is actually the first piece I wrote. Itachi is made of epic win.
[]-[]-[]-[]
Uchiha Itachi - Cheetahs
[]-[]-[]-[]
Fast
Deadly
Stealth hunters
Loving brothers
Power at a price
Quiet grace in each step
Sharp beautiful marked faces
Living swift brief lives of sorrow
[]-[]-[]-[]
Fast - The animal which achieves the fastest land speed of any living creature. The guy whose hand seal speed can confound a mature Sharingan.
Deadly - Predatory mammal. Both of them.
Stealth hunters - A cheetah does not simply run down its prey. It sneaks up on them, them closes the remaining distance with that famous speed. ANBU operatives are required to possess a degree of subtlety in carrying out missions, I should think, and the lack of suitably sneaky actions on Itachi's part can be attributed to the genre.
Loving brothers - Cheetah males may hold territory singly, or in coalitions of 2 or 3. Coalitions are common, and coalitions made up of brothers are common. They will hunt together, defend their territory together, and if they happen across any lady cheetahs, they all get the girl. Itachi and Sasuke haven't gotten that far, nor will they ever, but they certainly have an interesting dynamic, to say the least.
On an interesting side note, an established cheetah male accepting an outsider into his coalition is uncommon, but not unheard of. Kisame and Itachi work well together.
Power at a price - Cheetahs cannot sustain their top speed for long; overexertion would result in overheating, which could kill them. The Mangekyō Sharingan has certain famous drawbacks, namely eventual blindness, with only one deplorable method of cure.
Also, for a number of reasons, the cheetah gene pool is incredibly narrow and specialised. Which sounds like a certain clan known for over-reliance on their dōjutsu (eye techniques).
Quiet grace in each step - I've seen cheetahs. They really are overgrown cats, at least in the way they walk; you know, that effortless balance. Itachi strikes me as possessing the same elegance.
Sharp beautiful marked faces - Cheetahs have black markings on their faces, and are, again, big cats. Itachi has lines, and frankly, good looks.
Living swift brief lives of sorrow - Cheetah cubs tend to have trouble surviving past their first month, given the number of predators out for a good meal. Wild cheetahs generally do not survive past their twelfth year. And so long as they live, something died to feed them. Itachi died aged 21, having left behind one messed-up younger brother and an epic reputation in his kinsmen's blood.
[]-[]-[]-[]
Fave and review, dang it. If you do, I'll put up another one during the weekend.