1. A sandbag- These things are amazing. Besides the fact that, like kettlebells, they are portable, they offer great core training because of their instability. You can do cleans, presses, rows, squats, loads, rotations, you name an exercise and I'll bet you can do it with a sandbag. I'd go with about 1/3 of your bodyweight to start.
2. A 40'-50' thick rope- Holy hell. If you want a sick conditioning workout you should, nay, NEED to get a rope! Whipping this thing around with get your upper body jacked, gas your lungs, boost your work capacity, all while making girls go "Wow, thats a whole lotta man!"
3. A tractor tire-
While a bit hard to store, I believe the benefit far outweighs the scolding you will get from your parents/landlord. Building explosive power and getting good conditioning will be easier than getting a picture of Lindsay Lohan without panties on.
4. A sledgehammer-
Doing sledgehammer slams on your new tire will be one of the hardest exercises you've ever done. Adding this to your conditioning training will seriously help with upper body power and strength.
Well there you have it. Four things that can take your home gym from ordinary to "My lord I am all that is man!" Did I forget anything? Let me know in the comments!
Until next time, stay strong