How do you use X effectively?

There are a number of systems/weapons that I sell immediately when picking them up (or have never been able to use effectively when purchased). I'm curious to see if others use them effectively:
*Shield boost (big) - love the point-defense sized one, can't justify missing a weapon for more shield when there is an alternative available (use the small one instead)
*Escape pod - seriously, does anyone use this?
*Transporter - I want to like this. Just can't figure out how it makes more sense than an extra weapon.
*Missiles - I want to like these too. In all my playtesting you just need an absolutely stupid number of missiles for them to be effective (5 mounts with 3 shots per volley)
*Tesla Coil - interesting novelty?
*Energy Gatling - ditto.
*Flak cannon - fun at close range, but I tend to die very quickly in close-range combat.
*Bolter fighters - saw a thread where someone mentioned they like these. Haven't been able to make them work well for me (they seem to spend more time fishtailing than shooting)

For those who are curious - here is what I find works well for me:
*Weapons
**Death Ray - my weapon of choice
**Projectile cannon - pairs very well with energy cannon
**Repair beam / shield regenerator

Point Defense
**Bolters - when you add a burst upgrade they become very effective
**Shield booster - really, really like these late-game

Fighters
**Bolter Drones - pretty good all game
**Plasma Bombers - very effective once fully upgraded (4 ships instead of 1)