if you're a druid with access to this guy and fight hordes of tinies a lot, get this dude as a wildshape.

it's the best.

It has the possibility to have 72 hit points

Wouldn't it be 117 hit points? 6d10 is 60 + 12 = 72 + 45 = 117.

No, the HP can either be 6d10+12 OR can go with 45HP.

As a druid, my question is can you rampage to attack more than one enemy if you drop each consecutive enemy to 0 hp? For instance, if there were a bunch of enemies with low hp, say a hoard of rats, can I continue to attack one after another if each one is killed by my attack. 

You can only use 1 bonus action in a turn. You can only use rampage once per turn.

Yeah when I saw bonus action. I thought, awwww can only do it once. We’re about to fight a BBEG with about a dozen knights. Eek! 

No, 45 is the average

These make badass mounts, too. Gnolls, riding on giant hyenas as cavalry. Yeeee HAW!

meow?

can any type of animal be giant? (I need an answer).

Quote from 23Kinseys >>

can any type of animal be giant? (I need an answer).

 As long as you make a statblock for it, then yes.

cheeseburger 

My tabaxi Druid got one after helping some gnolls, and he’s a very good and unique mount and fighting companion for lower levels.

Is there a way to level these guys up?

My charater manged to tame one and its become their mount/pet, only problem is that ive gotten to a point where it can be oneshoted by most creatures we are battling

Here would be my idea for it to be larger than large, give the bite 2d8/10 damage, give it 60 ft movements speed, make rampage infinite (Highly controversial, do what you want) and of course make it beefier

Do these guys and the normal sized ones have a jump height; and would the Giant Hyena jump higher than the normal Hyena?

You mean you don't multiple the first number by what's in the () ?  It's not 45 (6d10 + 12) = 45 X 72 = 3240 HP?

is this a joke???