Champions' Special Item

Many champions have an item that specifically works for them because it fits their style.

(Nasus, Trinity Force) Nasus's Q affects his next AA, and sets the timer to 0. Trinity Force is activated by Siphoning Strike, and boosts the same attack. TriForce's cool-down is shorter than Siphoning Strike, so you know you can keep cranking out the obscene damage over and over again. This is why Nasus can severely mess up anybody's day.

(Garen, Black Cleaver) Besides the fact that it is a tanky item with CDR, it makes his Spin-to-Win demolish champions with several stacks of Cleave and bonus AD (Not to mention that it essentially adds Armor Penetration). Each time Garen hits you when he's spinning counts as a separate strike. Try eliminating him as an assassin when he's got this item.

(Darius, Black Cleaver) Same as above, but this plays into his passive. Each hit will cause enemies to be much softer of a target, leading to more brutal Pentakills.

What champ/item combos do you like/dread?