Secondary professions for an Assassin

Assassin Warrior
Assassin/Warriors get a lot of adrenaline, so you use adrenaline skills that do not require a great deal of attribute points. Skills in the Tactics line, and warrior skills without an attribute are good skills to go for. Skills such as Rush, "Fear Me!" or "Watch Yourself!" are good examples: with a lot of hits, you can continuously Rush or have 20 extra precious armor points, even with little to no attribute point investment. Fear Me is a great energy drain, but it requires some investment. However, with a lot of attacks, the energy drain is undenyably effective.

Also, the Assassin's primary attribute Critical Strikes can be very useful when wielding an axe or another Warrior weapon. The sheer damage of a Warrior weapon with a high chance of critical strikes amount to a ferocious combination. Axes and Hammers are the best choices in this case; they both have a big high-end damage, which affects the critical hit damage. Axes allow for a shield off-hand, and attack faster. Also, Axe Mastery has more skills that attack more than one oppponent. Hammers on the other hand do not require you to meet the shield's requirement, leaving you with more attribute points.

Assassin do not have any attack speed enhancing stances, and can thus greatly benefit from the Warrior skills Frenzy and Flurry. The Warrior skill combination Frenzy and Rush is particularly advisable.

Assassin Ranger
The Assassin Ranger, like the Warrior Ranger, yields many good skill combinations. Ranger is a particularly versatile class, and the Assassin primary can benefit from this.

Skills like Troll Unguent could supply some much needed healing to the class, and a pet can help the relatively frail Assassin absorb more damage, although the 8 sec skill recharge when a pet dies can kill assassins more easily than a warrior. The poison skills of the Ranger can supplement the quick, low-damage dagger attacks used by Assassin characters to increase damage output.

You can also use Tiger's Fury to boost your damage output, and there are several spirits can boost melee effectiveness (like Winnowing). There is also an Assassin skill, Exhausting Assault, which causes interruption and exhaustion; combined with the Factions skill Equinox (which doubles exhaustion in the area), the A/R would lock down spell casters.

Apply Poison, with a poisonous dagger mod, is a boon to the assassin, which hits quickly. (On the average, an assassin with 16 dagger mastery strikes once a second due to the chance of double striking). This will keep the defender poisoned for between 27 to 37 seconds, assuming the assassin keeps hitting. Combine this with Jagged Strike or even Sharpen Daggers, and you will be able to keep your opponent poisoned and bleeding continuously at the same time.

Because assassin critical hit skills such as Sharpen Daggers work based off critical hits only, Barrage damage can be improved with high critical strikes attributes, and can be used to add critical strike effects to enemies.

Assassin Elementalist
As there is a weapon upgrade that can convert the damage on an Assassin's primary weapon, namely daggers to lightning damage, use of the skill Glimmering Mark with this upgrade will allow the assassin to greatly lower vulnerability against Warriors and other Assassins.

Another theory would be to take several close quarter spells of a single element with you (like Shockwave and Aftershock) allowing you to deal a lot of damage to nearby enemies. You could also use their weapon enchantments to boost your overall damage output.

You can also use Earth Magic skills to boost your armor level and create wards to negate damage before it happens. The energy cost can often be prohibitive at lower levels, or high death penalty, however.

Another possibility is to use the Shrouded armor set, and utilize critical strikes and elemental hexes to debilitate foes. The skill Black Lotus Strike grants the user energy upon a successful strike, and can go directly into Twisting Fangs, thus doing an enormous amount of damage. With water hexes such as Blurred Vision, the warrior and assassin threat may be mitigated, and using possibly Mirror of Ice, threats from high-damage spells can be turned against foes.

Assassin Mesmer
The Mesmer skill Blackout can be used while all of your attack skills are recharging without penalty, and can also be employed in combination with Temple Strike to further lock down a foe. Illusionary Weaponry along with the Assassin's fast attack speeds can work for a high damage combo.

Distortion makes for a very effective defense skill when combined with the energy regeneration effect of points in Critical Strikes. Also, Physical Resistance and Elemental Resistance can boost an Assassin Mesmer's armor to levels comparable to that of Warriors.

Since dagger attack skills often cause conditions, Fragility is a good way to do extra damage to your target. In case of multiple targets, Epidemic can be used to spread those conditions.

An Assassin Mesmer can gain an advantage against other melee classes with Empathy and can be more effective against Monks with Backfire.

The Assassin Mesmer is excellent at running, especially with a buddy; with a 20% enchantment item and full attribute points in Shadow Arts, Shadow Form coupled with Arcane Echo and if with a friend, Arcane Mimicry, can produce a mostly unstoppable force.

Assassin Monk
Using the offensive spells Smiting Prayers of the Monk can enhance the offensive effectiveness of a melee Assassin. In particular, one could use Bane Signet which provides a knockdown effect and follow that up with the Assassin skill Falling Spider which will cause the target to become poisoned.

The Protection Prayers skill line of the Monk will allow a melee assassin to stay in the fight a little longer. Spells such as Reversal of Fortune and Spirit Bond would be a welcome addition to any Assassin's arsenal, preventing deadly spikes.

The Assassin has very little in the way of healing abilities. Shadow Refuge does not heal enough, Death's Charge has a very long recharge time. Healing Prayers offers several skills that help an Assassin stay alive. Vigorous Spirit and Live Vicariously are good choices, especially with a high Dagger Mastery attribute. Healing Breeze is also a solid choice because the total health healed is high even without very much Healing Prayers. Often an Assassin may find themselves out of range of their party's healer due to the use of a shadow step. This is when the additional healing is a excellent supplement.

Two other skills that the Monk brings to the table are the very popular Rebirth, which is often much better than Resurrection Signet in PvE, and the very handy Purge Conditions, which will allow the assassin to shake off nasty conditions such as blindness, bleeding and poison.

Assassins generally have trouble finding groups, and Assassins with Monk secondary even more so, since some players might assume that an Assassin with good healing capabilities is even less likely to play 'hit and run' than the average Assassin and just use the healing to try to tank better/longer.

Assassin Necromancer
Combining Necromancer and Assassin teleport skills as well as Necromancer touch skills coupled with a dagger, the A/N is an effective hit-and-run build. The Assassin skill Death's Charge teleports to an enemy and heals, which can quickly be followed by Vampiric Touch, resulting in great health gain. Assassins can increase their consistent damage through the use of skills such as Barbs, Mark of Pain, and Weaken Armor. Rigor Mortis may be used as a longer-lasting alternative to Expose Defenses to guarantee that chained dagger attacks find their mark. Another useful combo is Spinal Shivers/Shivers of Dread coupled with a set of cold damage daggers. Although you may lose a lot of energy this way, the fast attack speed of Assassins guarantees interruption of almost every skill the enemy uses.

Furthermore, the Necromancer skills Plague Touch and Grenth's Balance require no attribute investment, and both have handy effects for melee fighters. The use of these two skills exclusively from Necromancer means you can freely spend all your attributes on Assassin.

Assassin Ritualist
A popular PvE combo as it allows Guild Wars players to fight through the Factions storyline only once and unlock the skills for both new professions. This character can employ spirits before it engages and can then proceed into melee with a distinct advantage. Further, an Assassin Ritualist can use the Assassin's Aura of Displacement with a Ritualist's Item Spell such as Cruel Was Daoshen, drop the ashes in the midst of enemies, and teleport back out of danger. Ritualist weapon spells, such as Brutal Weapon, can also add significant damage to Assassin attacks, and is especially effective due to the Assassin's attack speed.

An Assassin can also utilize the Ritualist secondary for assistance skills such as Generous Was Tsungrai for healing, Resilient Was Xiko for condition removal, or Flesh of My Flesh for resurrection.

Assassin Paragon
The Assassin may use the Paragon second profession by giving the class much needed protection from damage. This may help the fact that the Assassin has relatively low armor and is considered a "soft target". By using the Paragon's various shouts, it also may help improve damage output, which would make the Assassin an even faster killer.

Assassin Dervish
The Assassin/Dervish can use its high level of critical strikes to gain maximum utility out of the powerful critical hits that a scythe is capable of.