Call of Duty: Ghosts, Battlefield 4, StarCraft, GTA V PvP, Super Meat Boy, are all great stress relievers of course.
But srsly, Oblivion or Skyrim are very good for stress relief. Finding a fun lobby for Garry's Mod is great. Avoid TTT and Murder if you are already stressed.
What's even better though, is to try games that you have not played in a long time again that will bring about nostalgia. I played Star Wars Battlefront: 2 again a week ago after 6 years and I had an absolute blast.