Useful Equipment

What workout equipment should you get? There are a few factors. Money is obviously an important factor. Space is another factor. Time also matters. And your goals play a part.
Right from the start let's scratch out machines. This applies to the gym as well as home. In fact, 90% of commercial gyms are made up of machines ( one of the main reasons I detest most gyms).Machines work individual body parts, not the whole body.This causes imbalances, one of the main reasons for injury. They also give a false sense of accomplishment , mainly because you don't have to use your stabilization muscles. You'll find it relatively easy to military press or leg press heavy amounts. Now try to clean and press or squat that same amount with free weights.No luck.You'll be lucky to use half the weight. Machines are in a set position, moving you through a fixed position, often sitting down. This isn't how you move in real life.This doesn't make you stronger. One of the best examples are those lat pull down machines. You may be able to do 20 reps with a reasonable amount of weight but try to do 20 pull ups. Again, you won't be able to. Machine exercises don't equal success in other activities.There may be a place for them in physical therapy but that's probably the only place they have any use.Plus they're usually way over priced.
One of the best and cheapest are dumb bells. They're also very convenient. You can take them with you almost anywhere. You can do almost any exercise with them.The best types are made of iron. They can range from as little as 1 lb up to 50+lbs.
Kettle bells are fantastic. Like dumb bells, they're pretty convenient to take. There are even a couple of exercises you can do which you can't with dumb bells ( the swing and clean). Because the center of gravity is in the middle unlike dumb bells ( which have even amounts on each side) this forces you to work harder.Grip , as well as ballistic shock from absorbing the hit of the kettle bell in the clean, is worked( good for contact activities like fighting,football,etc.).Depending on the work out as well as your skill and imagination, you can get a mixed work out of anaerobic and aerobic work out all in one.The only two drawbacks are the definitely not cheap price (although because of its versatility you can save a lot on unnecessary equipment,gym fees,etc.Also deals can be found on the internet) , as well as the fact that it takes quite a bit of good practice to become proficient in its use.
Dumb bells and kettle bells are great for moderate to high rep work outs,i.e strength endurance, either one exercise at a time or a circuit workout. Plus, because they're not as wide as free weights ( barbells) it's easier to do the Olympic snatch, which otherwise requires  a lot of shoulder mobility.They can even be used for maximal one rep strength although here it's a little more difficult.The weight has to be heavy enough,you have to remove one of your limbs from the exercise ( 1 arm, 1 leg dead lift for example) , you have to change the angle of the exercise ( seated military press with the legs spread out), or a combination of all three.
This brings us to free weights. Certainly, for maximal one rep strength they are the easiest and most useful tool. Lifts like the squat, dead lift, military press, and bench press are best done with them.They really work that slow,grinding,strength.All your muscles come into play. Try to overhead press even 50% of your body weight , let alone 100+%, without cleaning the bar from the ground to shoulder level ( an explosive, difficult task in itself), then pressing it overhead. You'll have to really grip the bar, tense your whole body, your legs will press "downward" into the ground,as the bar goes overhead all your stabilizer muscles, especially the abs, will be needed to get that bar overhead. Weights are the best and easiest for maximal strength.That maximal strength has been shown to be helpful in almost every activity, especially when you need that sudden burst of strength (  keeping your fists up in the final round,etc).Even in medium to long distance activities they can help. I'm proof of that.Having a good base in maximal strength will also help you if you choose to do high rep work in the future.Also, low rep ( no more than 5 if even that) heavy weight training if done properly can be quite safe.Because the reps are so low you'll be able to concentrate on form thus avoiding improper techniques which is what most often causes injury. This type of training also produces natural testosterone, as well as releasing growth hormone into your blood stream ( provided you're eating right and getting proper rest).Plus you won't have to spend hours in the gym. No more than 30minutes, if even that( much of the time will be spent resting between sets ).You can also do Olympic lifting, the snatch and the clean and jerk and the clean and press. These lifts also can be heavy although they usually tend to be sub maximal . These lifts are very explosive ( except for the press part).They can really help in explosive sports like sprinting. They can give an incredible anaerobic work out.Like power lifting, this is a low rep work out. The major problem is the technical nature of the lifts. You may have to start with just an empty bar ( I have) or even a broom stick. Professional coaching is definitely recommended.
The major drawbacks to weights are the price ( though again deals can be found), as well as the space that's needed. Also, if you want a squat rack or bench, factor that in. A small bedroom definitely isn't going to work.And obviously you won't be able to take your weight set with you on vacation.
Other useful equipment include tires,sledge hammers, and kegs ( beer drinkers are happy!).Obviously these aren't very cheap and practical for most people .Medicine balls and stability balls, along with them. suspension equipment like TRX ,bands,rings and Jungle Gym are also pretty good stabilization and endurance equipment. They're also very convenient to carry. A pull up bar that fits in a doorway is good if you don't have access to a ledge you can hang from. I've never used the Perfect Push Up or Perfect Pull Up so I don't have first hand knowledge although people I've talked to have said they're pretty good. Some people have even been forced to improvise, often with good results. The best example is our military. Guys in Iraq and Afghanistan have been seen in some cases using rocks, machine parts, and even their duffle bags for work outs. American ingenuity!
For those who live in snowy climates, if you have the money as well as the space I suppose a treadmill would  be good. Personally the few times I've been forced on a treadmill ( at a hotel near a crowded road) I definitely couldn't stand it. There's even a stationary pool! No way could I do that.
So skip the infomercial ads and the celebrities hawking the latest and greatest. Save your money on things that have been proven, often closer than you think.