Stompy Mooks

"Oh, that's cheating; sneaking up! Did you have your legs on silent?"

—The Doctor, Doctor Who episode "The Next Doctor", regarding the Cybermen.

Our hero is walking down a corridor in the Big Bad's ship/castle/compound, and suddenly he hears *THUNK THUNK THUNK*! He has just enough time to duck down a side hallway before a squad of Mooks walk past him. And thus our hero is saved by noisy footwear.

What our hero has encountered is a group of Stompy Mooks. Stompy Mooks are basically mooks who simply cannot be quiet when they move around, even if they tried. These can include anything from Robot Soldiers, heavily armored soldiers, or just normal, everyday soldiers with noisy boots. This is usually played straight to make the viewer understand exactly what's going on and why the hero just ducked down a hallway.

Of course, when the plot requires it, Stompy Mooks can be as quiet as church-mice.

Film

Lampshaded in Robin Hood: Men in Tights when the Sheriff calls in a bunch of guards in heavy, clanky armor to surround the protagonists.

Prince John: I hope it's worth the noise!

The Lo Pan's terracotta warriors in Big Trouble in Little China.

Literature

The Vogon guards in The Hitchhiker's Guide to the Galaxy.
Subverted in Harry Harrison's The Stainless Steel Rat. Jim diGriz is trying to escape from soldiers inside a building. He avoids one pursuer making noise with heavy boots, then another soldier coming from another direction with loud boots, and ends up in a meeting with the chief of the pursuers. He then learns that the soldiers had been ordered to herd him into the meeting with their stomping.

Live Action TV

The Cybermen from the Doctor Who new series are a great example of this trope. It's even Lampshaded in the episode "The Next Doctor", as seen in the page quote.
Jaffa, from the Stargate universe, are so notorious for this that you can be assured that in every hallway scene on a Goa'uld ship there will be some form of clanking. The Ori Crusaders do this too, but to a much lesser extent. As a funny note, the Jaffa actually cease clanking once they are freed from the Goa'uld.

Video Games

Inverted in the Metal Gear series. Walking too fast behind a guard makes him turn around and notice you, turning you into the Stompy Mook.
Inverted in the Thief series. Garrett, the main character, actually wears loud boots because he believes the guards to be complete idiots. Not without good reason, mind you.

Real Life

Soldiers marching in formation often count as Stompy Mooks.