Interesting to see the full variety of fuels used.
When I started one of my mentors got me started using cut up 100% cotton jeans with some green grass thrown on top. I like the cool smoke that this produced, but the sap/moisture from the grass gummed up the lid and made it harder to close. I did stick with this for quite a while, and the only drawback was that when I did my larger yard, I wanted my small-capacity smoker to go a little longer before burning out.
Recently, I switched to the dark side and tried some pieces of dried out hard and soft maple, along with the dead bark. I think I really hit on something with hardwood, because the dried bark lights with a candle lighter torch, and if you get it going well, it's really easy to get the dry hardwood going too, and once you throw the lid shut, it makes great smoke with that awesome hardwood smell. Pack the smoker full of chunks of this, and it will go for much longer than some of the other items, and still burns hot enough that it's easy with a few good squeezes of the smoker to get new chunks going. Squeeze repeatedly until you have a good high roaring flame, throw the lid shut, and enjoy your time with the bees!