Ambushes

Ambushes are when you hide in trenches in the tunnel with enemies coming down it. When the enemies are close to your trench, you jump out with a swuvle or shotgun and swiftly kill the enemy. This is a tactic used against unexpecting and naïve players, mostly minigunners. It can be a deadly skill when mastered and can result in an easy win.

Performing
To perform an ambush, you need to create a trench in a tunnel, preferably the most popular, or hide in one that's already there. Then you must wait for an unexpecting foe to pass by your trench, you can use your camera to look in the tunnel without revealing yourself. When the enemy passes by, you jump out and quickly kill the enemy with your swuvle or shotgun, swuvle is preferred but has a lower range.

Trivia

 * This tactic is fan made and has no official name.