sudo apt-get remove transmission-gtk --purge
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-2.6.35-22 linux-headers-2.6.35-22-generic
Use 'apt-get autoremove' to remove them.
The following packages will be REMOVED:
  transmission-gtk*
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
After this operation, 848kB disk space will be freed.
Do you want to continue [Y/n]?