Ghouls from Hellsing. Mindless, infinitely disposable, and created en masse by inexperienced vampires.
Mazinger Z: Baron Ashura's Iron Masks and Count Brocken's Iron Cross. They were mindless, obedient cyborgs Dr. Hell created using corpses. The former ones vaguely resembled an ancient Greek soldier whereas the later ones look like modern soldiers. Knowing who are their commanders, it is pretty logical.
The typical low rank Marines in One Piece. Luffy can defeat hundreds at once, and their role is just typically to showcase the abilities of a certain character (and freak out about how crazy he is,) then continue the attack so that they can get mowed down some more. True to form, they are frequently endless, for all intents and purposes.
Don Krieg's armada is an earlier example. With 50 ships and 5000 men, East Blue calls it an invasion force. The Grand Line? Target practice.
This gets played for laughs in the Straw Hat crew. Zoro has once dubbed Sanji "Pirate A". Sanji did not take his mook status well.
An interesting occasion comes up in the climax of the Enies Lobby arc, in which two hundred Marine Captains are sent after the Straw Hats. The Straw Hats are initially concerned about this, as that's the rank Smoker was when they last saw him. Fortunately, it turns out that Smoker's Cowboy Cop tendencies kept him at a rank far lower than what suited his skills, and the rest of the Captains weren't nearly that strong.
By the time a pirate hits the New World, an army of mooks is pretty much useless. Thanks to the ability "Conquerer's Haki" (which Luffy has), one can impose their will on someone, and, if their will is weak enough, knock them out. Luffy used this ability in the Fishman Island arc to knock out 50,000 mooks in one blast — and the only reason he didn't knock out the other 50,000 is because his crew needed someone to fight.
Pick any Gundam show. Chances are, there's gonna be a notable Mook from it. For just a few examples...
Mobile Suit Gundam 00 carries many Mook-like mobile suits within its roster, but the most notable would definitely be the Union Flag.
When some Ryozanpaku masters in Kenichi: The Mightiest Disciple tell Kenichi that he is not as good a fighter as he ought to be because he didn't defeat his last opponent fast enough, Shigure, who nurtures some sisterly feelings towards Kenichi, tries to defend him by telling them that the opponent threw too many mooks at him. This provokes the following responses from them:
Sakaki: (laughing) There's no need to count trash... I once took out a master who had over 100 underlings. Ma Kensei: I once slipped through 1000 soldiers and only took out the commander. Apachai: I once completely annihilated all my enemies and allies.
Terrorists, cartel goons, Nazis, mercenaries, yakuza punks, and other no-name bad guys tend to die in droves whenever the crew of the Lagoon Company or one of the many other Badasses of Black Lagoon swings into action.
Balalaika's Vysotniki are Elite Mooks. Most of them are nameless. They have no faces and personalities to remember, and have no storyline role apart from "Balalaika's muscle." Nonetheless, most of the above-mentioned badasses in the show recognize attacking them as nothing short of suicide, not the very least because Balalaika herself has a policy of coming down like the Wrath of God upon those who dare to hurt or kill them.