Pros: Nylon leashes practically last forever. They dry fast and you can wash them often. They can be found to be less than $3, such as on DogSupplies.com.
Cons: It depends where you clip the leash on the dog. Also, dogs who chew go through them pretty easily.
$3-7 on DogSupplies.com
Pros: This leash can be used to effectively teach a dog to come when called. See the video below demonstrating come when called using a retractable leash.
Cons: Does your dog walking in front of you mean that he is pulling? YES. A retractable leash allows your dog to walk ahead of you, and even if you don't feel he is tugging you forward, in his mind, he is taking YOU for a walk because he is the one leading the walk. Many people let the retractable leash stretch all the way such that when crossing the road, the dog is in the middle of the road while the owner is still on the sidewalk. I don't need to explain why that is dangerous. In addition, in emergency situations where you want your dog to closer to you, it is impossible retract the leash if you dog is running in the opposite direction from you. Also, the leash is very thin and can often times result in rope burn to your hands, legs, arms, and consumer reports have reported finger amputations by the retractable leash.
$30 on Amazon.com
Pros: You can use this for jogging without having to hold the leash in your hand. This is also an excellent training tool. You can use this to teach your dog to respect limits in your house if you don't trust your dog to free roam in the house. You can attach your dog to you and walk around the house with your dog in sight. Also, when training your dog outside, your hands will be able to deliver treats while teaching your dog to heel.
Cons: You always have to adjust the waist size if multiple people are using one lead. Also, if you make the leash to the shortest length, the dog's legs always gets tangled on the leash.
$25 on Amazon.com
Pros: It is a good tool to control your dog from lunging at other dogs or people, and easily control dogs from pulling. However, do not put constant pressure on the dog while the gentle leader is on him. Learn how to properly use the gentle leader before training your dog with it.
Cons: People on the street always think it's a muzzle, so they assume the dog is dangerous. I just tell them that the dog can still bite you if he wanted to. But it is unsettling that people think your dog is aggressive because of the "muzzle."
$11 on Amazon.com
Pros: This is great for training dogs to not pull, but not effectively for dogs that lunge. The front clip harness turns the front side of the body around when you stop as he is pulling. This teaches the dog that if he is pulling, his front body will get turned around.
Cons: First time putting it on may be confusing. There's alot of straps and multiple clips. But like many repetitive acts, it gets easier to put on each time.
$15 on Amazon.com
Pros: It is great for tugging you along on skateboards, bikes, and roller blades. They can use their entire body to pull you along.
Cons: The harness allows the dog to PULL. So don't use it if you don't want your dog to pull!
$4-17 on DogSupplies.com
Walky Dog-for Biking
Pros: When holding the leash in your hand and biking with your dog, he could easily pull you off your bike if he sees something in the perpendicular direction (yes, I have experienced that). This doesn't let them pull you and he will always run next to you. It is very simple to assemble, as shown in this video.
Cons: If you have a heavy dog, and he tries to pull head, the attachment on the bike tends to loosen up a bit and the walky dog stick will move towards your legs while you're biking. I need to tighten the screws everytime before I bike with my dog.
$49 on Amazon.com
Here is a wonderful article about the types of leashes out there by Whole Dog Journal. It is a very reputable journal that writes about positive dog training and holisitic ways of caring for your dog. This article talks about the responsible choices that dog owners make when choosing the type of training leashes available out there: Dog Training Equipment.