there are many unlockables in halo, there are:
-skulls, 1 to 2 on each level
-armor changes, depending on what you do (spartan officer, all skulls...etc)
-katana or sword-on-back, 1000 gamerscore (from halo only)
-maps, heroic maps for 800gamerpoints not score (new legendary maps coming out)
that's about it if you want specifics on armor requirements Google it
these are about it.....
halo 3 obviously
Halo 3: ODST is the newest of the two, but not the newest Halo game.
its not really necessary to look for unlockables. All you have to do is sing the songs on the game and certain songs let you unlock the songs without the codes.
The halo time line goes Halo Wars, Halo: Reach, Halo:CE (halo 1), Halo 2, Halo: ODST, Halo 3. Halo 3 and ODST are practically at the same time.
Halo 3 ODST is not for PC but Halo 1 and maybe Halo 2-3 are
After Halo 3 there was halo wars, halo 3 ODST, and Halo reach. A new company (not Bungie) will be making a Halo 4 and rumor has it there will be a remake of Halo Combat Evolved.
it goes halo, halo 2, halo 3, halo 3 odst and soon halo reach will be available
Halo Games: 1. Halo: Combat Evolved (Xbox, PC) 2. Halo 2 (Xbox, PC) 3. Halo 2 Muliplayer Map Pack (Xbox) 4. Halo Triple Pack (Xbox) 5. Halo 3 (Xbox 360) 6. Halo 3 O.D.S.T (Xbox 360) 7. Halo reach (Xbox 30) Other Halo Games: 1. Halo Zero (PC) 2. Halo: Custom Edition (PC) Future Games: 1. Halo Wars (Xbox 360) 2. Halo: Chronicles (Xbox 360) 3. Halo 3: Recon (Xbox 360)4. Halo 3: ODST (Xbox 360)
there are tons of unlockables
the same way in halo 3 because when you play halo 3 mythic it says your playing halo 3
in HALO 3 you are a Spartan and in HALO 3 ODST you are a Orbital Drop Strike Trooper (ODST)
The names of all the Halo games are (in order): Halo: Combat Evolved, Halo 2, Halo 3, Halo Wars, Halo 3 ODST, Halo Reach, Halo: Combat Evolved Anniversary, and Halo 4. In chronological order: Halo: Wars Halo: Reach Halo: Combat Evolved/Anniversary Halo 2 Halo 3: ODST Halo 3 Halo 4