I know many of you will think that Hecarim is tank only, but honestly I never play hec tank. Im always going with this build and it goes perfectly each match.

I believe hecarim is great at all phases, although he is the best at early games, since his ganking is so good.
Mid game is pretty much as early but its getting difficult cause youre still building them ad items, so you're basically like a glass cannon.
Late game is when you get the tank items - you deal massive damage ; great engage in tf ; you can instantly change the turn of tf by your ult and other AOE abilities. And also you are ******** tanky, about 3,7k hp with superb AD; High MR and ARMOR.

Basically you'll be the vital piece of teamfights in late game.

Pros
High mobility
Plenty of escape abilities
Very effective ganking
Easy jungle clearing
A very good passive
The best spam damage ability - Rampage
Fully AOE skills
Cons
If gets slowed you're pretty much dead meat
A little squishy until mid game
Not much cons since i <3 this champ and this build