Secondary professions for a Warrior

Warrior/Ranger

 * The Ranger line offers a few alternative IAS skills.

Warrior/Elementalist

 * Shock can be used as a snare and interrupt, however exhaustion will certainly be felt with a Warrior's low energy pool.
 * Grasping Earth can be used as a AoE snare to keep groups of enemies from kiting as efficiently.
 * The conjure skills, such as Conjure Frost can provide additional damage when wielding an elemental weapon for a very small investment of energy.

Warrior/Mesmer

 * Wise use of Physical Resistance, Elemental Resistance or elemental mantras can add additional survivability to solo or tanking builds.

Warrior/Monk

 * The condition and hex removal skills of the Monk close a critical gap in the warrior skill line. Skills such as Mending Touch, Purge Signet and Empathic Removal are good utility skills.
 * Despite the popularity, Healing Prayers skills are less effective then a warrior's self healing skills, and should be avoided. This is especially true of Mending, which is often considered a laughable build element.

Warrior/Necromancer

 * The most common usage of the Necromancer secondary is for condition removal via Plague Touch.

Warrior/Assassin

 * The Assassin has a wide range of snares and shadow steps that can serve a Warrior well. Shadow Prison is an outstanding skill in this vein.
 * Signet of Malice can provide free condition removal.
 * Dash is an excellent speed boost that also serves as a quickly recharging cancel stance for Frenzy.

Warrior/Ritualist

 * Sparing use of Weapon skills can benefit a Warrior; Splinter Weapon can be combined with Triple Chop or Hundred Blades. Ritualist primaries, however, far outclass Warriors at spamming weapon spells.

Warrior/Paragon

 * Remedy Signet may be used with no attribute points for a quick, energy-free method of condition removal.
 * Spears negate the warrior's primary advantage of heavy armor.
 * Many shouts seem tempting to a warrior, but are generally ineffective with a warrior's poor energy.

Warrior/Dervish

 * Many Scythe Mastery skills are general-purpose Melee Attacks (i.e. Rending Sweep) rather than weapon-specific skills, which allows them to be used with axes, hammers, and swords.
 * Warrior's Endurance can provide the energy required to spam scythe attacks, however, Strength provides only enough additional damage against soft targets to merely keep up with a primary dervish with a superior rune.