Who doesn't LOVE burpees? This is such a great body weight exercise that can be modified in so many ways. You can also add dumbbells, ankle weights, and/or even a weighted vest to increase the intensity.
I'm doing these challenge now but you can do also the 1 to 100 burpee challenge. Each day do one more burpee that the day before . I lost 8 pounds doing that. Example : day 1 burpee, day 2 burpee until you finish in day 100 : 100 burpees.