The most important features CIG promised

Arena Commander
Space fight module*: join with your preferred ship to fight with other players against ai-pirates or play in a deathmatch against other humans.

Star Marine
First Person Shooter module*: fight like in a regular shooter in different gamemodes on maps with gravity and zero-g.

Hangar
Have a look at your new and old ships in your personal „Spaceship Garage“-Module*

*Modules: during the alpha we join the different modules over the menu, later during the development and after release they are like a simulator at a computer in your hangar or your ship. So you have ingame access, without leaving the Star Citizen universe.

FPS
Fight in the universe or on the planet surface in first person perspective against your opponents from face to face with pistols, guns, grenades and other gadgets or…

Dogfighting
jump in your spaceship to increase your firepower, defense and mobility and terminate your enemies.

The Verse
A single universe containing 100 starsystems with about 400 planets we can land and explore (dont try this on a gas giant) connected through a giant single meshed serversystem.

Multicrewships
Big ships who need up to 30 people to run probably. But also medium ships need a pilot, turret gunners, engineers and shield manager.

Economy
90% npc driven will gurantee a stable economy system, but the players will still have influence on it.

Professions
a lot of unique professions which will work hand in hand. (example: explorer have to find ore, the miner will collect it, the refinery will process it and the fighters will defend the cargo haulers who transport the finsihed product). Every profession will bring his own challenge and depth to the gameplay.

Reputation
Your relation with npcs will change as longer you have contact with them. A good reputation will unlock new missions or better conditions for trading.

Subsumption
NPC with a daily routine, like working, shopping and sleeping, for a real living world.
Various roles: Bartender, Doctor, Entertainer, Nurse, Sanitation Worker, Security Guard, Shopper, Tourist
but you can also hire them as NPC Ship Crew for multicrewships.

Spectrum 
Game integrated communications platform with VOIP, forum and social media function to better organize corporations and stay connected with friends.

Death
Respawn?? What do you mean with respawn? A revive is possible but thats all, if you die your character is dead. Your new character will maybe the son or the daughter of your old one and he will get all his money and ship, but you lose some reputation on all of your npc contacts.

Groundstations
Build your on base on a planet to make more money or defend a tactical important area.

Bigbattle
Fight with up to 200 ships in a fair 100 v 100 battle or be the first person who is insane enough to start a 1 v 199.

Player-Triggered Universe-Level Events
To cataloge a new stone from planet boring wont change the verse  much. Discover a jumpoint to a new starsystem not only make you rich, but also famous like columbo. Everyone in the verse will know your name and your jumppoint.

Hacking/Electronic Warfare
If you want to steal a ship its maybe not the best idea to stop it with a torpedo. Hacking the enemy ship system and shut down the enignes sounds much better.

Full Mobiglass Functionality
The counterpart to the today smartphones. Perfect for making selfies and watching porn. Maybe it come with some additonal unimportant functions, like managing your inventory or request a rescue mission

Rescue/Recovery System
Even the bravest pilot prefer to use his ejections seat instead of exploding in their ship. But what now? You are in the infinite of the space. Maybe it would be better to pay someone for a rescue mission.

Full Health and Injury System With Mobility Effects
Your leg won’t heal in under 10 seconds just because you got a medikit. If you are injured you will need time to recover your character to his old capability.

Survival/Environmental Hazards and protection
Maybe you should wear more than a raincoat during radioactive acid raining hurricanes. So dont forget your protectionsuit.