I agree with puzzles - the 'reverse crossword' idea sounds quite interesting. I also do The Guardian Quick Crossword every day: I like it because it's not too easy or hard.
Browsing/posting on forums.
Certain videogames. RPGs where you can just wander aimlessly about the world map, doing dumb crap; platformers; racing games, puzzle games, etc. Don't like games with endless shoot-outs or battles usually, though there have been a few exceptions.
Nature/animals. It annoys me so much less than humans -_-
The last one is gonna be weird. Pre-surgery, when I had active Crohn's, I'd often go and lie on the floor in the bathroom. It was vinyl and the coolness of it was soothing. I also had a stricture (narrowing), which made food getting through difficult: but the sound and feel of it passing through was also oddly soothing. There'd be horribly uncomfortable pressure; a massive gurgle; relief - rinse and repeat for the next 2 hours. (Note: total obstructions are a different story. The guts really don't like it when food can't pass through at all.) To a far lesser extent, I get a similar thing with the ileostomy.