by Hilary Goldstein at IGN

June 19, 2007 - Multiple Xbox 360 achievement sites posted the hottest list on this or any other planet today. Halo 3's 49 achievements (for a total of 1000 Gamerpoints) were revealed by achieve360points.com, among others.

A few things can be gathered from the achievements (oddly enough, none of which are secret). For one thing, these aren't final. At least, the descriptors are not, because some of the achievements have placeholders on scoring requirements. We also now know there are nine chapters in the campaign. And the skulls are back. In Halo 2, a skull was hidden in almost every level. Finding it was sometimes tough. Sometimes a skull in Halo 2 unlocked abilities; now it unlocks achievements.

When asked to confirm the validity of the list, a Microsoft representative said: "Halo 3 is still in development and achievements are not final."

Name Description Points
1. Landfall - Finish the first mission of the Campaign on Normal, Heroic, or Legendary. 20 Points
2. Holdout - Finish the second mission of the Campaign on Normal, Heroic, or Legendary. 20 Points
3. The Road - Finish the third mission of the Campaign on Normal, Heroic, or Legendary. 20 Points
4. Assault - Finish the fourth mission of the Campaign on Normal, Heroic, or Legendary. 30 Points
5. Cleansing - Finish the fifth mission of the Campaign on Normal, Heroic, or Legendary. 30 Points
6. Refuge - Finish the sixth mission of the Campaign on Normal, Heroic, or Legendary. 30 Points
7. Last Stand - Finish the seventh mission of the Campaign on Normal, Heroic, or Legendary. 40 Points
8. The Key - Finish the eighth mission of the Campaign on Normal, Heroic, or Legendary. 40 Points
9. Return - Finish the final mission of the Campaign on Normal, Heroic, or Legendary. 50 Points
10. Campaign Complete: Normal - Finish the Campaign on Normal. 125 Points
11. Campaign Complete: Heroic - Finish the Campaign on Heroic (unlocks achievement for Normal, if not earned). 125 Points
12. Campaign Complete: Legendary - Finish the Campaign on Legendary (unlocks achievements for Normal and Heroic, if not earned). 125 Points
13. Iron - Finish the Campaign on Normal, Heroic, or Legendary, then find and claim this skull. - 10 Points
14. Black Eye - Finish the Campaign on Normal, Heroic, or Legendary, then find and claim this skull. 10 Points
15. Tough Luck - Finish the Campaign on Normal, Heroic, or Legendary, then find and claim this skull. 10 Points
16. Catch - Finish the Campaign on Normal, Heroic, or Legendary, then find and claim this skull. 10 Points
17. Fog - Finish the Campaign on Normal, Heroic, or Legendary, then find and claim this skull. 10 Points
18. Famine - Finish the Campaign on Normal, Heroic, or Legendary, then find and claim this skull. 10 Points
19. Thunderstorm - Finish the Campaign on Normal, Heroic, or Legendary, then find and claim this skull. 10 Points
20. Tilt - Finish the Campaign on Normal, Heroic, or Legendary, then find and claim this skull. 10 Points
21. Mythic - Finish the Campaign on Normal, Heroic, or Legendary, then find and claim this skull. 10 Points
22. Spartan Program Recruit - Win your first game in matchmaking to sign up for the Spartan Program (Online). 10 Points
23. UNSC Spartan - Earn your Sergeant rating to be recognized as a true Spartan (Online). 15 Points
24. Spartan Officer - Advance to the Spartan Officer ranks (Online). 25 Points
25. Two for One - Score a Double Kill with a single spartan laser shot in a ranked free for all playlist (Online). 5 Points
26. Too Close to the Sun - Destroy an enemy banshee with the spartan laser or missile pod in a ranked playlist or in campaign. 5 Points
27. Triple Kill - Kill 3 enemies within 4 seconds of one another in a ranked free for all playlist (Online). 5 Points
28. Overkill - Kill 4 enemies within 4 seconds of one another in a ranked free for all playlist (Online). 5 Points
29. Lee R Wilson Memorial - Score 5 grenade sticks in any ranked free for all playlist (Online). 5 Points
30. We're in for some Chop - Destroy an enemy vehicle with equipment in a ranked playlist or in campaign. 5 Points
31. Killing Frenzy - Kill 10 enemies without dying in any ranked free for all playlist (Online). 5 Points
32. Steppin' Razor - Score a Triple Kill with the sword in a ranked free for all playlist (Online). 5 Points
33. Mongoose Mowdown - Splatter an enemy with the mongoose in a ranked free for all playlist (Online). 5 Points
34. Up Close and Personal - Kill 5 enemies by melee or assassination in a ranked free for all playlist (Online). 5 Points
35. Fear the Pink Mist - Kill 5 enemies with the needler in a ranked free for all playlist or in campaign. 5 Points
36. Headshot Honcho - Kill 10 enemies with headshots in a ranked free for all playlist or in campaign. 5 Points
37. Used Car Salesman - Destroy a vehicle that has three enemies in it in a ranked playlist or in campaign. 5 Points
38. Marathon Man - Locate and access all Terminals in the Campaign. 40 Points
39. MVP - Earn the MVP in any ranked playlist (Online). 5 Points
40. Maybe Next Time Buddy - Board the same vehicle within 10 seconds after being boarded in any free for all playlist (Online). 5 Points
41. Demon - Score over X Points in the Campaign meta-game on the second mission. 10 Points
42. Guerilla - Score over X Points in the Campaign meta-game on the first mission. 10 Points
43. Cavalier - Score over X Points in the Campaign meta-game on the third mission. 10 Points
44. Askar - Score over X Points in the Campaign meta-game on the fourth mission. 10 Points
45. Exterminator - Score over X Points in the Campaign meta-game on the fifth mission. 10 Points
46. Ranger - Score over X Points in the Campaign meta-game on the sixth mission. 10 Points
47. Vanguard - Score over X Points in the Campaign meta-game on the seventh mission. 10 Points
48. Orpheus - Score over X Points in the Campaign meta-game on eighth mission. 10 Points
49. Reclaimer - Score over X Points in the Campaign meta-game on the final mission. 10 Points

Source = http://xbox360.ign.com/articles/797/797773p1.html

You can see the list with achievement images at Xbox360Achievements.org