Trauma Probe

Trauma Probe is not supposed to proc more than once every 3 seconds. Against a single target, that appears to be true, but against multiple foes, it can use up several charge at once - up to 4, I've seen, against 4 foes - allowing it to do all of its healing in 13 to 24 seconds (according to my stopwatch).

This means you're doing more healing in a shorter amount of time (higher HPS). And since Trauma Probe is your single most efficient heal with an ammo cost, you can use it more often in long, drawn-out fights against multiple foes that will tax your ammo.

Don't listen mindlessly to those who say Trauma Probe should never be used except before combat or if you have nothing better to do. While it's a poor choice when you're trying to do as much healing as possible as quickly as possible (i.e., HPS outweighs ammo conservation), it's your number one tool - other than free heals - for conserving ammo in long fights (averaging 3221 healing per ammo for me, compared to 2301 for Kolto Bomb hitting 4 targets, or 1913 for AMP with Preventative Medicine).