1. I've found that new experiences are a passion of mine. Whether good or bad, I want to experience as much as I can. It wasn't until I had my heart crushed that I understood half of the art I've ever seen. The first time I ever tasted shiso was a revelation that I think I posted on this site somewhere. Now I grow Japanese green shiso and Korean red shiso and also have some umeboshi in the fridge. Seeing new parts of the world, food, interesting people, philosophy... really anything that gives me that well I've never felt like that before.
2. Love or(as TaraK says) that significant other. There is nothing like that feeling of wanting to give anything to make another person happy and knowing they feel the same.
3. Wilderness, there is nothing like being on top of a mountain or in the middle of a virgin forest with the nearest person over twenty miles away to put things into perspective. Most often, your journey to get there you will encounter many of the most beautiful things you've ever seen.
4. Music, Jmak, while Miles Davis makes me cry out of beauty, Mingus, Dylan, Bowie, Tim Hardin, Leonard Cohen and a whole bunch of others, well, as the thread title says, make life worth living.
5. Quality, yeah, so what, I read Robert Pirsig and liked it. Suck it.
Quality = Beauty
Quality = Sustainability
Quality = Integrity