A great way for Vanguards to save themselves from imminent death.
It's very much worth the time to upgrade the Charge power (exclusive to Vanguards) fully. Each upgrade increases the shielding benefit you get from activating the power.
At rank 4, you'll be able to choose between Heavy and Area charge. Choosing Heavy will give you %100 shields upon activation, as well slowing down time to allow you more time to get to cover.
This is an extremely useful tactic when Shepard is low on health, protecting him from further damage, and giving you some respite from the enemy onslaught.
It also enables you to fly across the room to whomever you're targeting, allowing you to to escape if you're being mobbed by husks or just generally surrounded by enemy fire.