Secondary professions for an Assassin

Assassins are highly aggressive, focused, damage dealers, better for hit and run skirmishes then drawn out tanking or back-line sieges.

Always remember, when choosing secondary skills, that native skills often have better synergy with the profession's purpose, interact better with the profession's other skills, and benefit from runes.

Assassin/Warrior

 * Skills such as "Fear Me!" and Whirlwind Attack syngergize with the extra adrenaline from fast dagger attacks.
 * Assassins do not have any attack speed enhancing skills (Excluding the PvE/Nightfall-only Critical Agility). Flurry, Flail and Tiger Stance can increase the rate they can pull off an attack chain, as well as increase their overall DPS.
 * Wild Blow to cancel important stances.

Assassin/Ranger

 * Barrage damage can be improved with high critical strikes attributes, adding bonus damage to attacks, energy bonus, and effects from skills like Critical Eye, if you use Barrage with Sharpen Daggers, you can spread bleeding in mobs.

Assassin/Monk

 * The Protection Prayers skill Mending Touch is a good spell to remove risky conditions.

Assassin/Necromancer

 * Hex spells, particularly from the Curses line (Parasitic Bond), can be used to drive many attack chains involving the foe being hexed. Although, many primary Assassin Skills, most notably Siphon Speed, can serve the same purpose.

Assassin/Mesmer

 * Arcane Echo can be used to chain Shadow Form when running or soloing.
 * Epidemic can be used to spread conditions.

Assassin/Elementalist

 * The knockdown from Shock can drive an attack chain, though it is no longer as popular as other skills such as hexes to drive the attack chain.
 * The Conjure Spells (Conjure Flame, Conjure Lightning, Conjure Frost) can increase the overall DPS of an assassin.

Assassin/Ritualist

 * Sparing use of weapon spells such as Warmonger's Weapon can aid an Assassin in battle, although weapon spamming is best left to Ritualist primaries.

Assassin/Paragon

 * If you use the skill "Go for the Eyes!" it will drastically increase your chance to critical and get the energy gain. It is also beneficial because you do not need adrenaline for Assassins.

Assassin/Dervish

 * The Earth Prayers and Wind Prayers attributes provide little benefit for a dagger-wielding primary Assassin, however Critical Strikes synergises well with a scythe.