The new cultist event/enemy/npc.
Guide and Nurse sitting on Chairs.
Portals from the
Portal Gun in action.
New armor Cenx was wearing.
Dyed Bee Mount
Dryad and Wizard new action animations.
New progress bars during world creation.
New Eclipse monsters presented by Crowno.
One of the four
Terraria is scheduled for release on June 30th, 2015. This may be the last update that 1.3 update works on personally. During the development of Redigit 1.3, Redigit began preliminary work on one or more new games. The developers and Yoraiz0r will continue updating Skiphs Terraria during and beyond 1.3.   This version is said to be "better", rather than merely bigger with an inflated item count. [forums 4] [reddit 1]
official changelog for Terraria 1.3 was made available on June 27.
Details on 1.3's "spoiled" features thus far are listed below.
Arkhalis, A new sword that is obtained just like the Enchanted Sword. It behaves like no other sword in the game, as it only swings back and forth.
, a Meowmere sword that fires cat projectiles that leaves a rainbow trail, and make cat sounds. [forums 9]
added to each Sinks furniture set. [forums 10]
. Portal Gun [other 1]
Cultist costume vanity set. [forums 11]
and Honeyfall Block . Wall [forums 12]
: Offers a 1/3 chance of not consuming ingredients when crafting Alchemy Table Potions. [forums 7]
. Vine Rope [forums 13] [forums 1]
. Web Rope [forums 14]
. Sticky Dynamite 
. Nail Gun  [forums 3]
. Royal Gel 
crafting material, possibly used to craft Bouncing Pink Gel Bombs, Pink Glowsticks that float in water and Pink Slime Block, among other things. [forums 9]
. Magic Water Dropper 
allows teleporting to another player's location by pointing to them on the Wormhole Potion Minimap. [forums 9]
Gender Change Potion. [forums 6]
Flask of Frost, a new Flask. [forums 9]
Frost Bullets. [forums 9]
. Laser Machinegun [forums 9]
Charged Laser Blaster. [forums 9] 
and associated Granite Blocks Furniture set. [forums 9]
and associated Marble Blocks Furniture set. [forums 14]
, for growing Planter Boxes Herbs as portable items. [forums 15]
Target Dummy for testing weapon effects. [forums 15]
Rainbow Torch. [forums 14]
Yo-yo, a [forums 16] Flail-like weapon with multiple variants, including the Hel-Fire and the Terrarian. [forums 1]
Sundial. [forums 14]
. Shadowflame Hex Doll  [forums 3]
. Martian Conduit Plating [forums 3]
Martian Costume Pants. [forums 3]
, a Bee's Knees bow dropped by Queen Bee that fires 3 homing bees that bounce on walls twice and get destroyed on contact with third wall. Each bee does around 10-70 damage. Replaces normal arrows into three bees. 
Blackhole Beater, a new ranged weapon. [forums 2]
, a loot item dropped by Treasure Bag Bosses in Expert Mode . 
Flying Saucer pet/ minion. [forums 1]
Star Wrath, a stronger version of Starfury. [forums 1]
Daybreak, a spear projectile weapon. [forums 1]
Phantasm, a bow capable of firing up to 3 arrows simultaneously; the arrows retain their special properties, and have a chance to be recovered. [forums 1]
Solar Eruption, a flaming flail-like weapon. [forums 1]
Solar Fragment, dropped by Solar enemies. [forums 1]
Deadly Sphere pet/ minion. [forums 1] Super Healing Potion, the health equivalent of Super Mana Potion, restoring up to 250 health. [forums 1]
New Dyes: Living Rainbow, Living Flame, [dev 1] Chlorophyte, [tweets 1] Gold, [forums 13] Negative, [forums 3] Pixie, Wisp. [tweets 1]
Campfire variants crafted using the various Torch types, including the Rainbow Campfire crafted using the new Rainbow Torch, which cycles colors similarly to [forums 15] Rainbow Bricks; and the Demon Campfire, crafted from [forums 2] Demon Torches, with similar red-purple-blue color-change effect. 3 new
Mounts including a Drill Mount, (a late-game, futuristic digging vehicle) a Unicorn Mount, and a weird alien-like salamander thing. [forums 4] [reddit 1] [forums 1] New : Banners Green Slime, Ice Slime, Red Slime, Purple Slime, Jungle Bat, Illuminant Slime, Illuminant Bat, Giant Bat, Snow Balla, Lava Slime, Crimslime, Possessed Armor, and other unknown banners. [forums 14]
General item mentions
New summon items (
Minions/ Pets). [other 2] New summonable light sources, including a Crimson ball and a mechanical lantern.
[forums 1] New
Wings, including one that looks like Mothron's. [forums 1] New
Trophies.  A fourth
liquid. [forums 17] A new
Hook. [forums 9] A new
Block with gradual light-up function. [forums 18] A shield based on
Eye of Cthulhu.  New information display
Accessories that show current weather with wind speed/direction, number of nearby Chests detected, number of nearby enemies detected, number of nearby rare creatures, current movement speed, current total Fishing power, current effective damage-per-second (DPS), current Moon phase, and more. [forums 14] [forums 1] Additional Minecart variants, as well as a dedicated Minecart slot, and an obtainable [forums 3] Minecart item. [forums 1]
NPCs now respond to enemy attacks in unique ways.
[forums 1] The
Dryad casts a leaf shield spell that harms enemies, using a new casting animation. The
Wizard casts a spell that harms enemies, using a new casting animation. The
Nurse drinks potions when her health is low. The
Tax Collector hits enemies with a cane. The
Skeleton Merchant throws bones. The
Guide shoots enemies with a bow. The
Arms Dealer fires a Minishark. Its unknown if other NPCs such as the Merchant will respond to enemy attacks.
Events have progress bars. [dev 1] Dedicated equipment slots each for
Pet, light source, Mount, and Hook, which can each be dyed. [tweets 4] [forums 1]
Weapons can be used while riding mounts. [forums 23]
Minion Modifiers. [forums 9]
Fishing Pole Modifiers. [forums 9] Starting outfit options at character creation.
[forums 24] Improved character selection screen.
NPCs have better AI and animations, will no longer stand in front of Chests to block access, and sit in Chairs. [forums 4] [reddit 1] Characters have "spring in their step," especially during running. (The body area isn't "bouncing" anymore)
[forums 4] "Cleaner" and "smarter" starting areas on world generation.
[forums 4] Smart cursor will build stairs.
Liquid flow looks more fluid and less "blocky." [forums 13]
Lava and [forums 2] Water have new decorative dripping animations. [forums 1] Quick Loot, which works like "Quick Stack" but in reverse, pulling from
Chests only the items that have existing stacks in the player's inventory. [forums 9] Quick Stack to all nearby
Chests (without having to click them individually). [forums 14] Favorite
inventory slot: Mark an inventory slot as a "favorite" to keep its item from being trashed, deposited, or sold. [forums 9]
Signs can be read by merely hovering the cursor over them. [forums 9] Can now craft using ingredients from open
Chests without having to move them into the player's inventory first. [forums 9]
Minimap shows other players who recently died in Multiplayer. [forums 9] Upon your own
death, the total amount of coins you dropped is displayed. [forums 9] Showcase acquired items to other players in multiplayer chat.
[forums 15] Progress bars during world generation, colored to signify
Corruption or Crimson.  A fifth (pink) team for
Multiplayer. [forums 14] User interface tweaks and enhancements: new icon graphics, highlighting on mouse-over, new display for information accessories like the
Watches and GPS. [forums 14] Information accessories like Watches and GPS have their effects shared with nearby players in
Multiplayer, with toggle option. [forums 14] Camera mode, for taking screenshots of areas that are larger than the screen can display.
[forums 14] [forums 1]
Dyes are more visible. [dev 1] Re-designed Water
Fountains and one possible new Fountain. [forums 25] Steam integration for
multiplayer, allowing you to join steam friends' worlds. [forums 3]
The Underworld is naturally lit, and has a new background. [forums 2] The
Lava meter displays above the character instead of on the upper-right corner. [forums 2] Biome backgrounds updated, and each will have multiple possible backgrounds. [forums 26]
Platform stack limit increased to 999 (from 99). [tweets 1]
Living Wood Chests always contain a Living Wood Wand and Leaf Wand. [tweets 1] Updated most ore graphics.
The Axe drop rate increased from 1/200 to 1/50. [tweets 1]
Voodoo Demon increased spawn rate. [tweets 1]
Bunny Mount no longer incurs fall damage. [tweets 1]
Sunflowers now glow at night and give a "Happy" buff that reduces monster spawns and increases movement speed. [forums 6]
Jellyfish have a shock effect when they attack.  Updated some of the NPC sprites.
[forums 27] Updated a number of Potion sprites.
Staff of Regrowth additional uses, possibly including growing Jungle Grass on Mud, moss on Stone, and speeding Tree growth. [forums 9] 
Coins have new spinning animation and new pickup sound effect, along with new inventory sprites. [forums 9] Some
Tombstones have new sprites, and a possible new Tombstone added. [forums 14] Flying pirate ships added to
Pirate Invasion. [forums 1]
Enchanted Sword weapon will now be found in its own "shrine" area generated on world creation. [forums 4] Many items have been buffed, including: Staff of Earth, Golem Fist, Christmas Tree Sword, Flamelash, Trident, KO Cannon, Flower of Frost, Flower of Fire, Flower Pow, Frost Staff, Keybrand, Magnet Sphere, Possessed Hatchet. [forums 6]