Years ago, the Canon S45 was my everyday camera. As years went by, I moved through a series of digital compacts until getting a Canon 30D DSLR, which became my everyday camera. Then it was the Canon 5D Mark II with 24-105L and 35L. This yielded great images but was increasingly cumbersome.
When the Leica M9 was released, it became the main camera I took everywhere, along with a Summicron 50 and Nokton 35/1.4. But I always enjoyed smaller cameras, so the Ricoh GRD III was the camera I always had with me, regardless of anything else. Whether I had a Fuji X100, Ricoh GXR or Olympus E-M5, I always had the GRD III.
When the GRD III broke, I replaced it with the Ricoh GR. I also had a Panasonic LX7, which I loved, but that broke too, along with the GR. Later, I got a Panasonic LX10 to replace the LX7, but cameras with extending lens barrels have started to give me the willies, as that is their main point of failure.
Nowadays, the camera I take everywhere is the Sony RX0. Waterproof, crushproof and silent, it's the perfect pocket camera for me. Every compact camera that has failed had an extended lens barrel, so the RX0 is great in the lack of that feature. While I still take out the M9, and also the Panasonic G9 or S5, the RX0 is the one that is always there, all the time.