From Diablo Wiki
The hand crossbow is a class-specific item that can only be used by the Demon Hunter.
Unlike the normal two-handed crossbow, the hand crossbow is a one-handed item which the Demon Hunter can dual wield, or equip with a shield or quiver. Hand crossbows have the fastest inherent firing rate of any ranged weapon in the game, but slightly lower damage per shot in compensation.
Many Demon Hunters prefer hand xbows due to their faster firing rate. Shooting more quickly allows for more damage output in a short time, and also means that Hatred Generator skills will restore more resource in the same amount of time.
That said, not all Demon Hunter builds desire IAS. Some play styles rely on big hitting attacks with a heavy Hatred cost, and pay for them with Hatred regen or other means of resource regeneration other than Hatred generating skills.
Legendary Hand Crossbows
There are a variety of legendary and set versions of Hand Crossbows, all of which can be viable for the end game since D3v2 and RoS introduced item scaling so all gear scales up to the level of the character who finds the item (assuming monsters in the game are around that character's level). Thus Demon Hunters tend to use whichever bow, xbow, or hand xbow the yfind with the best damage, the best stats, and especially the best legendary affix.
See the individual pages for specific stats on each item. Items over level 61+ can only be found in Reaper of Souls.
- 8) Helltrapper A5 Cache
- 8) Izzuccob
- 29) Balefire Caster
- 31) K'mar Tenclip
- 41) Deadeye - Crafted
- 50) Dawn
- 60) Calamity
- 60) Danetta's Revenge - Set
- 60) Danetta's Spite - Set
- 60) Natalya's Slayer - Set
- 60) Hallowed Judgment - Crafted Set
- 60) Blitzbolter - Crafted
- 70) Hallowed Condemnation - Crafted Set
Demon Hunter Dual Wielding History
At Blizzcon 2010, hand xbows could only be dual wielded. The bows came in a pair, and looked something like you see in the paperdoll mock-up to the right. A Demon Hunter could only equip both at once, or neither; it was not possible to equip just one hand xbow along with a quiver or one-handed weapon or a shield.
This was thought to be a balance issue; the hand xbow was the fastest firing ranged weapon in the game, but as a trade off they had to be used two at a time, trading defense for offense. This may not be the case in the final game though, as Bashiok explained while answering some forum questions in November 2010. 
[Can the Demon Hunter use] two separate and unique one hand crossbows w/ different stats on them?
Bashiok: Yes, that is in. A lot of work is being done right now on demon hunter weapons so some things are still up in the air, but dual-wielding one handed crossbows in each hand, each with their own unique enchants and gems, etc. is now in the game.
So, one could now wield a one-handed crossbow in one hand, and a shield in the other?
Bashiok: Potentially, but some things are still up in the air
I do wonder what other classes will be able to use 1 handed crossbows.
Demon Hunter Cinematic
The Demon Hunter makes extensive use of dual hand crossbows in her introductory cinematic, devastating a horde of demons with the weapons.
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