Parasites: More for their use in minimising defensive attrition, so your heavily attacked wormholes you have to replace ships less, then actually getting ships in other instances. Their ability to convert turrets is remarkably annoying at times, since you have to keep deleting the damned things since they're usually not in any useful place.
Tachyon Fighters are really good as well. Though it's much more for their de-cloaking ability then their actual damage output. Given all the other options are either slow, starships, or immobile, having something in your pack of ships that actually means you can avoid loosing a large chunk of your forces to mines, especially with the mine-obsessed AI, is rather convenient.