Engineer gives mind control head enchant, that one gives passive stamina too
Saronite bombs are pretty cool when you have no keys to press. Not sure of they even give some threat or scale with threat multipliers. Cobalt Frag belt enchant is more of a PvP enchant I guess(shares CD with Saronite bombs(6mins iirc). Belt enchant is useless, good thing is that it's useble togeather with extra socket enchant.
Hand Armor enchant will not allow you to use Armsman, extra armor is way better deal since that treat enchant is useless.
Sure injectors are nice and can save in a pinch, not for tanks tough, better use Idestructible potion.
Greatest boon is Nitro Boosts, it even says "overpowered" in description man
Also things like Mailbox, repair, reagents, access to bank anywhere to swap those sets. Jumper cable knife is nice too, saved a lot of time in few instances.