Here is a guide to all of the known exotic weapons and armor in Destiny 2.

Kinetic Weapons

• MIDA Multi-tool
• Strum
• Rat King
• Sweet Business
• Vigilance Wing

Energy Weapons

• Coldheart
• Hard Light
• Fighting Lion
• Riskrunner
• Graviton Lance
• Skyburner’s Oath
• Sunshot

Power Weapons

• D.A.R.C.I.
• Merciless
• Legend of Acrius
• The Prospector
• Tractor Cannon
• The Wardcliff Coil

Titan Armor

• Helmet
  • Insurmountable Skullfort
  • Mask of the Quiet One
• Guantlets
  • ADC/0 Feedback Fence
  • Doom Fang Pauldron
  • Synthocepts
• Chest Armor
  • Actium War Rig
  • Crest of Alpha Lupi
  • Hallowfire Heart

Hunter Armor

• Helmet
  • Celestial Nighthawk
  • Foetracer
  • Knucklehead Radar
• Guantlets
  • Mechaneer’s Tricksleeves
  • Young Ahamkara’s Spine
• Chest Armor
  • The Dragon’s Shadow
  • Lucky Raspberry
  • Raiden Flux
• Leg Armor
  • Lucky Pants
  • Orpheus Rig
  • STOMP-EES
  • Hunter Cloak

Warlock Armor

• Helmet
  • Crown of Tempests
  • Eye of another World
  • Nexarec’s Sin
  • Skull of Dire Ahamkara
• Gauntlets
  • Karnstein Armlets
  • Sunbracers
  • Winter’s Guile
• Chest Armor
  • Starfire Protocol
  • Wings of Sacred Dawn
• Leg Armor
  • Lunafaction Boots
  • Transversive Steps

Here are more Exotic item details as revealed by the leaker:

• There are 51 exotic items total, this excludes possibly hidden exotics. For example, ones from the raid and those like the Black Spindle etc.
• 18 exotic weapons, including 16 new and 2 old ones (modified)
• 11 exotic armors per class for a total of 33, so 7-8 new and 3-4 old ones per class
• and of course no “3 of coins” (not sure what he means there?)
• 6 strikes. One is exclusive to PS4 so 5+1, each of the strike contains exclusive strike loot + normal loot
• Armor mods are obtained in “bright” engrams and through trading with Banshee-44
• There’s over a hundred legendary weapons to loot, not including the armors, of course
• In the guide it says 6 available (note: he’s still talking about strikes) on the 6th of September but more to come, so I imagine that they’re gonna add more with updates. If I’m not mistaken, Deej had already talked about ten-ish.

So at least 51 Exotic items in total, along with 6 possible extras which will be made available at launch.