Muscles worked: chest, shoulders, triceps, hamstrings, lower back
This exercise is often done in the military, it requires you to start in a piked position (as pictured above).
Then you lower your nose to the ground while maintain your arched position.
Right before your nose hits the floor flatten yourself out as if you are trying to slide under a bar and keeping your hips low to the ground drive your head upwards until you are looking straight ahead.
Finally, do everything in reverse until you are back at the starting position. That was one divebomber pushup.

Muscles worked: quads.
If you are anywhere near a wall then you have all you need to destroy your quadriceps with this intense exercise. There isn’t much to explain, but if you can’t do one leg, do two.

Muscles worked: calves, hip abductors
While there is probably no need get into the “how” of jumping jacks, as we assume everyone is at least familiar with the mechanics, unfortunately familiarity breeds contempt and this workout is often overlooked due to its percieved simplicity. It can be an amazing warm up though, and if you are having trouble finding space to run/jog, a thousand jumping jacks make for an excellent cardio workout.

Muscles worked: abs
This exercises is mainly for your abs. Although normal crunches are super effective by themselves, there are numerous variations that you can try in order to hit your oblique abdominals as well (bicycle crunches above).

Muscles worked: quads, calves, hamstrings
This is a powerful lower body workout. If you failed to find that perfect elevated surface for your box jumps, fear not, jump squats to the rescue. With your hands behind your head proceed with a regular squat and once you reach your lowest point explode upwards, jumping off the ground. Repeat.

Muscles worked: lats, traps, biceps, rhomboids, deltoids
Depending on your grip (overhand, underhand, spread) you are essentially working out your entire back. This exercise requires something for you to grab as shown above.

Muscles worked: quads, calves, hamstrings
This is a dynamic exercise that only requires an elevated surface. Once you figure that part out you’re ready to break a serious sweat. Just jump up onto the box/park bench/bed/etc. and then jump down again. Repeat this until your lower body is 'destroyed'. However if you can't find an elevated surface, you can always try out 'Jump Squats' mentioned above.

Muscles worked: quads, glutes, hamstrings
This is probably one of the best leg workouts you are going to get without a gym and luckily its pretty straight forward. All you have to do is take a large step with one foot and bend your knee to a 90 degree angle (as shown above). Although you can walk forward with each lunge you don’t have to. You can stay in the same spot if you want and just keep switching legs. Heck, you could even do these in the shower. But please, don't try this on a slippery surface

Muscles worked: abs, back, shoulders No, this is not planking. In order to do this exercise you have to actually hold yourself up off the ground. You can also modify the exercise by turning to the side and holding yourself on one elbow. This is one of the best things you can do for your core.

Muscles worked: traps
Your traps (neck muscles) are one of the hardest parts of your body to target without having some sort of weight in your hands. In fact, unless you can find some parallel bars, hang from them upside down, and do “inverted pullups” you are going to need to improvise. Probably the easiest thing you can do is stuff your suitcase and use that as a stand-in dumbbell *lol*. B