Reverse Arm Fold

The physical inverse of the Badass Arm-Fold, where the arms are folded behind the back. The hands may be clasped together just behind the waist (more common in the West), or gripping the opposite forearm higher up (more common in the East). This posture generates strong connotations of patience and consideration.

There are four basic character types who use this, for their own reasons:

Martial artists, especially the Old Master, who will hold this pose constantly while his hands are not occupied, unless he's a monk, in which case one hand will hold a prayer position in front of his chest.
Old people of the Asian persuasion in general, who take the same pose but lean forward as if for balance.
The Contemplative Boss. See the picture on that page for an example.
Military personnel, while on duty but not actively engaged in some activity. This stance is known as Parade Rest in the US and At Ease elsewhere.

Examples of Reverse Arm Fold include:

Anime

Mercenary Tao and less often Master Roshi, in Dragon Ball.
You sometimes see Gendo doing the Western version in Neon Genesis Evangelion.
- The Eastern version is practically Rei's trademark pose: grasping right forearm with left hand with right arm hanging straight down. No one else in the show does it, just her. It suits her rather closely and heavily emphasizes her femininity if she does it while wearing a plugsuit.

Comic Books

A signature pose of Adrian Veidt, who qualifies for both the Contemplative Boss and martial artist reasons.
A signature tic of Darkseid, Superman's awesome foe, is to go arms behind the back while doing some Exposition about how whatever the heroes can throw at him will mean nothing, or stuff like that. The counter to Superman's World of Cardboard Speech in Justice League Unlimited is a good example, as is his beating of both Superman and Supergirl in Superman/Batman: Apocalypse.
Lex Luthor, one of Superman's other Arch Enemies, is also fond of this pose.

Film

Darth Vader from Star Wars is sometimes seen doing this.
From Kill Bill, Pai Mei, as per tradition, holds this pose almost constantly when his hands are not in use.
Morpheus does it all the time The Matrix when he is not kicking ass. His variation particularly stands out because he's frequently gripping his arms at the elbow. Note that this isn't particularly comfortable or relaxing, especially if you're a reasonably well-muscled guy in a bulky BadassLongcoat, so either it's simply Rule of Cool, or it's emphasising his flexibility and badassery that he's able to relax in this pose.
- This particular variant of the pose is typically identified with the Old Master, so doing so suggests his mentorship to the rest of the crew as well as the general badassery required to make the pose work.
In The Lord of the Rings adaptations, Gandalf does this on the rare occasion that he's not clutching his staff or a pipe.

Literature

Vetinari, as a Contemplative Boss, is stated to do this whenever he stands in front of his big picture window.

Live Action TV

In early seasons of Star Trek: Deep Space Nine Jadzia Dax walked about with her arms behind her back, to demonstrate the "old man" that was inside her.
Spock In Star Trek TOS uses this pose many times in the second season onward.

Music

The back cover of The Black Parade album depicts some of the members of My Chemical Romance in the pose.

Video Games

Master Chen in Shenmue walks around hunched over like this, but wow, that old guy can dodge a punch.
Old Master Wang Jinrei of Tekken gained one of these during his intros circa Tekken 5.
Citan Uzuki is frequently shown doing this.
Master Xehanort does this a lot, but as with the Master Chen example, he's not as frail as he looks.
President Max adopts this pose when discussing Matters of State.
Dawn of War: Imperial Guardsmen do this when capturing a point.