Pilots from the Republic Military School's Center for Combat Studies are known for their creative approach to battle tactics.

Faction - Hardener To Use - Ammo to use against
Amarr Navy - EM / Thermal - EM / Thermal
Blood Raider - EM / Thermal - EM
Caldari - Kinetic / Thermal - Kinetic
Concord - Em / All Dmg Types - Thermal
Drone - All 4 - EM
EOM - Kinetic / Thermal - Thermal
Gallente - Kinetic / Thermal - Thermal
Guristas - Kinetic / Thermal - Kinetic
Khanid - Em / Thermal - Thermal
Minmatar - Thermal / Explosive - Thermal
Mercenary - All 4 - Thermal
Mordus - Kinetic / Thermal - Kinetic
Sanshas Nation - EM / Thermal - EM
Serpentis - Thermal / Kinetic - Kinetic

Sensors:
Gravimetric (Caldari)
Ladar (Minmatar)
Magnitometric (Gallente)
Radar (Amarr)


Depends what you're trying to achieve.

Turrets

Pulse lasers for rapid fire, short-medium range.
Beam lasers for long range high alpha lower DPS.
Taychons (a type of beam laser) for very long range with high alpha. Extremely difficult to fit.

Crystals
(In order of range, short to long)

Multifrequency
Gamma
Xray
Ultraviolet
Standard
Infrared
Microwave
Radio

Different crystals have different EM/Therm damage ratios. Long range Crystals do less damage. Some crystals require more capacitor than others. Faction crystals break with usage like t2 crystals, although they last about 4x as long.