Drinol

Summary
The Drinol are Covenant bosses that did not make it into Halo 2 and it is unknown if they will be featured in future products. It should be noted that a large Flood form has been found encoded in the Halo 2 disc. in the same way as the Engineers of Halo 1, this could be the infected form of a Drinol.

In the Behind the Scenes DVD, Drinol are described as huge beasts that are kept contained and segregated from the other forces. When enraged in phenominal strength, they are used to smash enemy vehicles.

In the Conversations from the Universe booklet found in Halo 2: Limited Collecter's Edition, an Elite refers to something called the "Sharquoi". Many assume that it means the Drinol.

From a Bungie Weekly What's Update:

Q: What's a Sharquoi? A: Very freaking dangerous.

A Gamesradar article has this to say:

How about this for a Halo 2 creature you've never heard of before: a Drinol Beast, a sort of hairless, grey monster with one eye - although there are other drawings of it with two eyes so you can't take for granted that it's going to make the final game.

Marathon Connection
Bungie enjoys placing links to their previous game franchise Marathon into Halo.

From a description of an enemy in Marathon:

''The Hulk is an enormous and rather slow creature, but it is incredibly strong. The science report indicated that it had no body fat, and therefore had to be fed often to keep it active. One crew member reported seeing one of these creatures pointing to itself and mumbling "Drinniol" right before it "picked Johnny up by the shirt and crushed him against a pillar".''

Images
It is now a mere render shown for speculation.