Ingame Username Change Mod 1.8, 1.7.10, 1.7.2 let you can change your ingame username. This mod does'nt work in online mode servers.

How to use:

• First install the mod like any other mod(non-forge)
• Now launch your minecraft with the mod click the button with a lock
• Now you will see a text box here you can put another name (max 16 chars) click the button called Change Nickname and done