I could not come up with a top 10 list for anything to save my life. Even top 10 beers would be a struggle. I agree with Brian that this discussion would benefit from a little focus because the topic is a little broad. So.......

Best time to go backpacking in the desert? Fall, Winter, and Spring. Cooler temps, the snakes are not out as much (but if it is warm they will be out), and in Spring there are the flowers.