Nothing happens other than getting the achievements and trophies in modern warfare 2. But in modern warfare 1, you get to unlock certain cheat codes that can be used during the game.
You can obtain new titles and emblems but that is all, everything else such as weapons and challenges are reset.
Challenge: "Free-for-all Victor: I" - Place first, second or third in 3 Free-for-all matches. http://callofduty.wikia.com/wiki/Callsigns For all Titles and Emblems.
You unlock the museum, an extra level displaying all of the levels off the campaign.
Call of Duty World at War, Modern Warfare, Modern Warfare 2, Black Ops, and Modern Warfare 3 all have online multiplayer.
Unlock the challenges for them.
to get all emblems you need to complete a certain of challenges for each weapons, which is really hard...
you unlock it by doing multiplayer it just matters how much kills, or falling, and random things you do
yup
No, all your guns are reset to the same as you were when you were level 1. The only thing you unlock when prestiging is emblems and titles.
Complete challenges and level up.
Your face thats the answer
heres one with emblems and titiles http://www.se7ensins.com/forums/modern-warfare-2-discussion/156442-callsigns-and-emblems-pic-list.html and heres how to get them http://www.se7ensins.com/forums/modern-warfare-2-discussion/156444-callsigns-and-get-them.html
you have 2 send a certain message and it unlocks all tittles emblems and golden desert eagle
You gain titles and emblems by completing certain challenges on multiplayer, check your barracks for the challanges. Here is a list of all the titles and emblems for call of duty modern warfare 2 on the Mordern warfare wiki: http://callofduty.wikia.com/wiki/Callsigns
That question isn't very specific, but I can tell you this from experience. You can mod your gamertag, you can hack prestige levels and unlock all callsigns and emblems, you can also use a jtagged xbox to use aimbot.
you level up and earn them all