Secondary professions for a Ranger

Ranger/Warrior

 * Warrior attack skills that use energy benefit from the Ranger's primary attribute, Expertise.
 * Rampage as One is used often with Energizing Wind for constant IAS and movement speed boost.
 * The classic Bunny thumper is effective in PvP.

Ranger/Elementalist

 * Elementalist spells like Conjure Flame can be combined with Barrage to deal extra damage.

Ranger/Mesmer

 * Echo chains can be useful when trapping.

Ranger/Monk

 * Mending Touch for condition removal and Purge Signet for multi-hex removal.
 * Rangers have efficient self heals, and should not invest in Healing Prayers.

Ranger/Necromancer

 * The "Touch Ranger" takes advantage of Expertise's effect on touch-range skills. This combined with ranger defensive stances and speed boosts make a powerful build with decent armor ignoring damage and potent healing.
 * Plague Signet and Plague Sending can handle conditions well.

Ranger/Assassin

 * Signet of Malice is an effective condition removal.
 * Expertise assassins are quite rare, Repeating Strike as one of their favorite skills.

Ranger/Ritualist

 * Weapon Spells such as Splinter Weapon and Brutal Weapon can work well with a bow, and combine with Barrage. Nightmare Weapon and Dual Shot create a potent health spike.

Ranger/Paragon

 * Some Paragon shouts and Barrage can prove effective, but are very difficult to balance.
 * several adrenaline Spear attacks in combination with Apply Poison can be an effective way to spread conditions.

Ranger/Dervish

 * A bow ranger can take advantage of enchantments like Ebon Dust Aura, Harrier's Grasp or Attacker's Insight.