Machinist's Mate AKA Mechanic: Often the burliest, but also on my boat the MMs had the highest percentage of WoW players. For reference, this was during BC and WotLK.
Engineering Laboratory Technician: A subset of the Mechanic, they're the ones who handle the water chemistry of the reactor, and monitor radiation levels. They're generally hated by mechanics since although they technically are capable of doing their job - and thus could/should be supporting their watches - they usually claim the need for independence. They're also generally liars.
Electrical Operator AKA Electrician: While in theory their job is to run and maintain the electric plant, in reality their job is anything that other people don't want to do/can't manage. They're masters at adaptation. I have personally assisted the Electrical Leading Petty Officer (as Reactor Leading Petty Officer) in troubleshooting and repairing the diesel generator control panel, various sonar equipment, heaters, etc. What also infuriates the electricians is that due to weird rules, while they're allowed to babysit the reactor while it's shutdown (called, appropriately, Shutdown Reactor Operator), they can't operate it at power. This, despite the Reactor Operators frequently being of lower intelligence and ability.
Electronics Technician AKA Reactor Operator / Propulsion Plant Operator: Basically God's gift to mankind, except for the dumb ones. Definitely the twitchiest of the bunch, and a solid amount of us are almost certainly on the spectrum. The job alternates between utter boredom (as it turns out, nuclear reactors are extremely stable at steady-state conditions), excitement (drills involving recovering the reactor following an emergency shutdown), and hatred (any maintenance activity involving the steam generators).