Cardio flat out blows balls. Yep, that's right, big balls, and not smooth one's like Jishu's either.

Ok, back on topic. If you're going to do cardio...what's is called.....HIT cardio. High Intensity Training. Sprinting with minimal breaks will keep your heart rate sky high and will force your body to recover like it would after a weight training session meaning you'll be burning calories long after you're done. Also, it doesn't take forever to do, I used to full out sprint for 30 sec, walk for a minute, sprint 30 seconds, walk a minute. I would cover one mile in sprints, so about 8-9 times meaning a workout was over in under 15 minutes, and damn, that worked really well.

If I got bored of running I would either
A: swim
B: jumprope like Rocky
C: chase a chicken around like Rocky