What's worse than a cannibal monster eight feet tall? One with a chainsaw. And a sack of grenades.
In Quake, an Ogre is a chainsaw-wielding creature that uses a Grenade Launcher as its long-distance weapon. Unless gibbed, they drop a Backpack containing 2Rockets upon dying.
Strangely, while all other Monsters (except for the Grunts and Enforcers in the Base levels) feature melee or supernatural forms of attacks, the Ogre is the only one with relatively modern weapons. On the Ogre's shirt is a small Quake symbol.
Alone, an Ogre is easy to kill. Get close enough so that it tries to swing its chainsaw, then run back and take it out with the Super Shotgun. If you're far enough away that he fires grenades at you, take him out quickly with either the Nailgun, the Grenade Launcher, or the Rocket Launcher.
In the company of other enemies, Ogres serve as a distraction due to their grenade launchers. They'll usually stay away from you and toss grenades while you're fighting off an enemy. Find an area where you are out of their range and take on the other enemies beforehand. Despite its size, the Ogre is weak and its attacks are easy to avoid, making it a lower priority in a firefight than, say, a Fiend or a Shambler.
With Quad Damage, hitting an Ogre with a rocket is a one-hit kill - just be careful not to get too close, otherwise you'll be killed by the splash damage.
Ogres only aim horizontally. This means that an Ogre at a higher location will rarely hit its target unless its grenades fall to their level, and at a lower level its attacks will miss entirely. In fact, an Ogre will often cause splash damage to itself or other nearby enemies (even other Ogres). Exploiting this weakness is cost effective and useful.
Ogres often provoke other enemies into monster in-fights due to their reckless use of grenades; also, because of their large frame, it is easy for long-range attacks from other creatures to be intersected by an Ogre. At close range, they can kill a Scrag, a Knight, and a Grunt with relative ease; they can also cause significant damage to a Death Knight, a Fiend, a Vore, or even a Shambler. If an Ogre happens to provoke a Zombie, it will continuously revive itself and serve as a constant distraction (even though it uses a Grenade Launcher, it is weaker than the player's and thus does not cause enough damage to gib a Zombie), thereby creating an opportunity to kill both creatures from a distance using the Rocket Launcher.
Their grenades can cause small amounts of damage to each other. This can be useful if you can maneuver one Ogre into the crossfire of another for a long period of time. With the right angle and a little bit of patience, you can simply wait for them to take each other out. It is possible for an Ogre to commit suicide if an excess of his Grenades explode too close to himself, but this is a rare occurrence and requires perfect timing.
The Ogre can still injure a player, even if both are on opposite sides of a wall, when using the chainsaw. Oftentimes, the Ogre can be tempted to continue swiping after the player has hidden behind the wall, resulting in the player taking damage even though an obstacle exists between him and the Monster.
Circle Strafing works very well against the Ogre; make sure there is enough room so the grenades don't bounce back.
Originally, the Ogre was wielding an Axe and a shield, and was called Axe Ogre. The original description stated: "The lowest of the low, this is the most basic monster in Timequake [original name of the game] next to the Glop. It also has the most character: pisses on dead bodies (yours included), chuckles when something dies, and occasionally has flies buzzing around it. He also has a shield that will block attacks."
According to John Romero, the Ogre's chainsaw was present from the initial concept, and his axe was the first weapon that they modelled into his hand. However, Romero wanted the Ogre to have the ability to assault at range, which he could not do since both of his weapons required close combat moves, thus they inserted the grenade launcher into his hand instead.
Kevin Cloud spent a lot of time animating the Ogre compared to all of the other models.
↑Interview with John Romero Where he states, ‘The chainsaw idea was there from the inital [sic] concept and the axe was the first weapon we modeled into his hand. The only problem was that both his weapons required close combat attacks and i wanted a distance attack - so we put the grenade launcher in his hand instead. One thing I wanted to have the Ogre do is laugh and piss on your corpse after he killed you. We ran out of time...’