Stun

Stun is an ability to daze one or many nearby enemies in place rendering them immobile and unable to attack for a short time.

Barbarian

The Barbarian class in Diablo III has a few stun abilities and passives that can be tweaked through the skill trees.

Critical Attack

In the Battlemaster Skill Tree, the Barbarian has the Critical Attacks (passive) that may be upgraded up to 15 ranks (BlizzCon 2008 demo). It may increase bonuses on stun abilities.

Ground Stomp

Ground Stomp is an active skill from the Juggernaut Skill Tree that knockbacks and stuns all nearby enemies for a length of time.

Stunning Blows

Stunning Blows is a Tier 3 passive skill that grants all Juggernaut Skill Tree abilities a 3% chance to stun attackers for 2 seconds.

Wizard

The Wizard in Diablo III has a few stun abilities that may stun enemies.

Charged Bolt

Charged Bolt is a Tier 1 active skill that causes critical hits from lightning damage to stun targets for 2 sec. This ability is found in the [Storm Skill Tree].

Thunderstruck

Thunderstruck is a Tier 1 passive skill that increases the critical hit chance of all lightning spells by X%. This means the chances to stun targets for 2 seconds increases when you apply extra points to this skill. Thunderstruck may be found in the [Storm Skill Tree].

Electrocute

Electrocute is a Tier 3 active skill that benefits from critical strikes and Thunderstruck to cause enemies to be stunned for 2 sec.

Improved Charged Bolt

Improved Charged Bolt is a Tier 3 passive skill that increases the number of bolts released by your charged bolt spell. At this tier, with a good amount of points in Thunderstruck (increases critical strike on lightning attacks) the stun chance is increased. Good against multiple enemies.