You are hardcore... I try to use only the body weight: push-ups, chip-ups, rope skipping, frog jump, etc. They work well too and less likely to get injured.
BTW, any good neck mucle exercises to share?
No... I haven't heard or find any good neck exercises other than just moving your head...
But I lift weights with my trapezius muscles, 210 lbs, it works the neck a little bit.
As for your body weight exercises, here are some good ones.
box jumping (jump on a higher level)
1 hand push-ups
push-ups on a ball, not half, full ball (curved surface, works pecs and abs)
dips
hand stand push-ups (push-ups with your head down, feet in air, works your shoulders and abs)
Punching (punch very fast and explosive, works your shoulders and pecs)
Superman (I don't really know how you call this but just lay on a flat surface stomac down and do the superman, works your back)
There isn't any good ways to work your legs without weights (even box jumping we normally use weights) since your legs are the largest muscles on your body and your body weight isn't enough to give them a work out. So good luck with that.
Hope this helped.
Oh I forgot to mention, for those people who don't want to use weights, Swimming is the best way to go. It will not only work all of your muscles, but the water will also shape your body (in a good way), it will work your lungs and for some people, there are women half naked.