Not an exhaustive list by any means, and not in any particular order. Just as they occurred to me:

1. Practicing Fernando Sor and Mauro Giuliani studies on the guitar.
2. Sitting in the nearby park and watching the antics of the squirrels.
3. As frogprince said, listening to Bok, Trickett, and Muir.
4. Listenng to Brahms' Piano Concerto No. 2 (and much other music).
5. Laying in a warm bath and gazing at the ceiling.
6. Waking up in the morning as my wife, still half asleep, rolls over, lays her head on my shoulder and puts her arm across my chest.
7. Watching some television:   good dramas, like "Bleak House" or "The Inspector Lynley Mysteries," or well-written, outrageous comedy like "Two and a Half Men," or science programs such as "Nova," especially ones dealing with astronomy and cosmology.   
8. Singing about a half-dozen songs (with or without guitar) just for my own enjoyment, where no one else can hear me (singing for others is a different kind of enjoyable experience).
9. After sending Sam Radding a check for nearly $400.00 to build me a slightly customized GO-GW nylon-string travel guitar, looking at my latest bank statement and seeing that I can well afford to indulge this particular GAS attack (it should be here in about a month).
10. Finishing a nice piece of writing a couple of days before our writers' group meets (which reminds me. . . .)

Don Firth