While playing my Tactical Escort, I like Mask Energy Signature for science. It makes doing non-combat space missions extremely quick and easy. It also comes in handy for PvP and other uses. For tactical I use Cannon Rapid Fire, High Yield Torp and Torp Spread. My Engineer uses emergency power to shields.
Engineering Crew. 30s of resists, alternate 2 of them per 45. And heal up any hull damage that slips past the lower capacity regen shields.
For ground, phaser turrets. I am an engineer myself and run with 2 engineers in my away crew. Will probably go 3 at some point if I can get away with not having a tactical officer. My engineering BOffs get trained in Phaser Turret I, II, and III, since they can actually summon one of each. Mass pew-pew!
Reverse Shield Polarity. Now that I have it, I'm not sure how I ever lived without it.
Had the same reaction to Emergency Power to Shields in Beta. I'll have to try this one.
For ground combat, I was pleasantly surprised by the shield generators. I'd expected disappointment because I've seen a lot of negative posts on it, but my original BO engineer had it so I figured I'd give it a shot. It's not only a decent buff but an aggro magnet. Even if it only lasts for 15 seconds or so because the mobs light it up like a Christmas tree, it gives you time to pick off enough targets to really change the dynamics of a fight, while regenerating your shields after the alpha strike.
Another nice bit is that both of these can be taken by the same Engineer BO, meaning anybody can get them on any character.