File extension ttarch is used by following file type(s):

File extension ttarch file type description:
Sam & Max game data file

The TTARCH file extension is associated with the computer adventure game series Sam & Max originally developed by LucasArts now by Telltale Games. The .ttarch file contains Sam & Max game data including graphics, models, level maps, sounds etc. The TTARCH file format is also used by other games developed by Telltale.

that open ttarch files:
Sam and Max Complete Collection (Microsoft Windows)
Telltale Explorer (Microsoft Windows)