Secondary professions for a Ranger

Ranger/Warrior

 * Rampage as One combined with skills from the line of Hammer Mastery, provides quick adrenaline gain. These rangers are often referred to as "Bunny-Thumpers".

Ranger/Monk

 * Judge's Insight can provide a considerable damage boost for Barrage, however the combo is too expensive to sustain.
 * Mending Touch is useful for condition removal and Purge Signet is useful for multi-hex removal.
 * Rangers have efficient self heals, and should not invest in Healing Prayers.
 * Resurrection skills such as Rebirth are useful on a Ranger Primary's, as they tend to have better survivability than other professions and can save a party from a near Party-wipe.

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.

Ranger/Mesmer

 * Echo chains can be useful when trapping.
 * Fevered Dreams can be used to spread AoE conditions.

Ranger/Elementalist

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

Ranger/Assassin

 * Signet of Malice is an effective condition removal skill.
 * Expertise assassins are quite rare as they are not very effective. However, those that do exist, often use the skill Repeating Strike.

Ranger/Ritualist

 * Weapon Spells such as Splinter Weapon, Nightmare Weapon and Brutal Weapon can work well with a bow. They combine with Barrage and Dual Shot to create a potent damage spike.
 * Binding Rituals are affected by expertise, though Primary Ritualist's are often better Spirit Spammers.

Ranger/Paragon

 * Spear attacks are affected by Expertise, thus allowing a ranger to spam them.

Ranger/Dervish

 * Rangers can successfully use this build to create a new form of condition dealing. By using the elite Ebon Dust Aura on a ebon bow, in addition to the other condition causing enchantments the dervish has to offer, this ranger has the ability to cause serious damage and provide successful defense against warriors and assassins.
 * Heart of Holy Flame and Barrage are useful against undead foes.