Three that help me feel chill are Sea Wolf (a homebrew for the 2600), and any version of Bosconian (including the Namco Museum versions for modern-ish systems, the plug in play version included with Pac-Man, and Kobo Deluxe for Linux), and Burgertime or any of its variations (Beef Drop for Atari 5200 and 7800 or Burger Space for Linux).
I think Sea Wolf is the most powerful, however, for inducing calm. I noticed that it has the same effect on my son and my dad, who are 62 years apart. All three of us can play it for quite a while, having fun, and feeling chilled out. Good times.