best damage against rats:

drones* - EM so use lasers

blood/angels* - EM, so lasers ftw

sansha's nation - look above

guristas/caldari* - kinetic, but nobody cba to wait for missiles to do the damage, besides rails suck so use lasers

serpentis/gallente* - thermal or kinetic, well in this case melt them with lasers, (rails suck even moar)

angels/minmatar* - explosive, use lasers, cba to train projectilies anyway

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footnote:
*don't use missiles, ccp said they cause lag so you might expect that missiles will be nerfed into oblivion in the near or distant future.