Command & Conquer: Red Alert 3/Ambushing

Ambushing is the use of usually fast and manueverable units to attack an enemy with speed and surprise.

Allies
Mirage Tanks — The Allied Mirage Tank is the ultimate anti-armor ambusher. It's combination of stealth and firepower is a highly dangerous foe. It can wait for an enemy to pass by, and then fry them with its spectrum cannons.

Soviets
The Soviets don't have a real ambusher on land, because they mostly rely on strength and attrition. However, the Sickle can use it's Flea Jump to jump on top of unsuspecting enemy infantry. The Mortar cycle from Uprising can also do some level of ambushing. At sea, the Akula Sub can suprise enemy vessels with it's deadly torpedoes.

Empire of the Rising Sun
The Empire of the Rising Sun can use the transforming abilities of some of their units to their advantage. For example, a MiG might attack a Chopper-VX, and then the VX would switch to Striker VX form and blow the MiG out of the sky. Or a Cryocopter might start freezing a Mecha Tengu, then the Tengu would switch to Jet Tengu form and destroy the Cryocopter. However, this could be countered by a combination of units, such as Twinblades escorted by MiGs, or Vindicators/Cryocopters defended by Apollos, or Chopper VX's guarded by Jet Tengus.

Yari Minisubs — On Sea the Yari must surface to fire but in large groups can decimate the most strongest ships when they ambush the enemy ships.

Sea Wings — Sea Wings only need to surface to fire if they plan to ambush aircraft with their missiles or fly into the sky and shoot enemy infantry.