Blood
I think it started when I was in the Navy. You got some extra liberty or something if you gave blood, so I did. For years I kept it up, especially when I started working in High Tech. GenRad had a Bloodmobile show up during work hours, and you were excused from work for an hour while you donated. Juice and cookies were an added treat, but some went way beyond that. When I worked at Credence in Milpitas, I got wind of a blood drive at a Nestle warehouse in Fremont. I showed up at this huge plant full of chocolate, coffee, tea, the aromas where stunningly delicious. After I was all done I was handed a bag full of candy and treats courtesy of Nestle. God, that one was sweeet! I'm certain I gave several gallons of blood, although unfortunately I didn't keep track. I gave blood in Oregon too, a church between home and work offered a convient place once a month to donate as it was on the way home.
I don't do it anymore, but it was fun while I did. I doubt I'll ever need much blood, but you never know. At least I was there for other folks, maybe somebody will be there for me.