Yes you can. Just select the "Invisible" mode. Then if oyur friend is online, just let them know you're online by possibly saying "Hey" or "What's up" And you can chat, while being invisible to others.
there are website which they use like http://www.scaninvisible.com
no moving in multiplayer mode but in maps that have 'ghosts' or invisible characters
Well as a server owner I know the only way is to run the server in offline mode. When it is in online mode(default) the server checks to make sure every account is premium. You can play on a server if online mode is set to false. This is a check mojang has put on to stop pirating on minecraft. So if you can't join the server is running with online mode on.
no there isn't an online mode of ac2 as far as I can see
http://www.scaninvisible.com
the online mode on call of duty:modern warfare3 is a 12
go on multiplayer and then you will see infrastructure mode
Go to www.google.com/talk and download Google Talk. You can fiddle with settings to automatically turn it on when you start the computer. *You can't be on invisible mode if you're on Google Talk at the same time.*
it has three singleplayer campaigns, a skirmish mode, and an online multiplayer mode.
you need to be connected to be in offline mode. obviously.
Yes, change your status to invisible mode.