Co-Washing, AKA washing your hair with ONLY conditioner

What It Is
It's pretty self explanatory, washing your hair with only conditioner. That's right, no shampoo.

What It Does
It cleans your hair gently, leaving your scalp and hair less stripped of moisture. It may not be enough to get out super sticky styling products but it will wash out almost everything. Yes, it really does clean your hair just fine.

Who Should Try It?
It is most popular with people that have curly hair and chemically processed hair. I would recommend it to anyone concerned with dryness, brittleness, and/or breakage. Some people that struggle with greasy hair found relief co-washing so it might be worth a try for those that struggle with oil. It may not be best for certain scalp conditions that require medicated shampoo. As someone that struggles with hereditary scalp eczema I found co-washing has alleviated a lot of my symptoms. Those will dyed hair will likely love it because NOTHING (aside from not washing at all) comes close to the co-wash's color saving power.

Products
There are a lot of products on the market specifically marketed as cleansing conditioners. They're really not that special and you can cleanse with just about any conditioner. The only thing I recommend avoiding is silicones. A conditioner that contains silicones will cause build up and will make your hair feel heavy, dirty and gross if not washed out with shampoo... which is what we are trying to avoid. Many so-called cleansing conditioners are full of silicones. Many cleansing conditioners will also tell you to use a ton of product, "30-50 pumps" every freakin' wash. Aw hell naw, don't buy into that crap and use just enough to completely coat your hair. Just work it in, leave it in a few minutes if it has penetrating natural oils, then rinse it out.

I suggest experimenting with different conditioners until you find one (or more) that you like for cleansing. You can also cleanse with one conditioner and then condition with another more moisturizing conditioner afterward.

Co-Washing Favorites
Suave Tropical Coconut 
It's not super moisturizing but does a great job for cleansing. It's silicone free and super inexpensive. The consistency is a bit runny so it's easy to work into your hair and scalp. For me, I need to follow with a more moisturizing conditioner.

Tresemme Naturals
Another inexpensive silicone free conditioner. I find this more moisturizing than the Suave one.

L'Oreal EverCreme Cleansing Conditioner
If you can find it (it's been discontinued) grab it! The only place I still find it at is Harmon's. This is my favorite cleansing conditioner. For me this product works as a single step, I don't need to moisturize afterward. I also don't need to add any anti-frizz serums or leave in conditioners afterward. It cleanses beautifully, removes any and all stubborn styling products and whatever else gets stuck in my hair. Also it totally restores my hair after it's been bleached. SO SO SO annoyed it's been discontinued. The only negatives I have to say about this (other than it not being available) is how little product you got for the price.

As I Am Coconut CoWash
Very easy to work into your hair due to the slightly runny consistency, similar to the Suave product. This stuff is very moisturizing and I like to leave it on for 20 minutes as a deep conditioner. This is a really nice product and is particularly recommended for those with curly hair or chemically processed hair. Never had any issues with buildup with this product.

EDEN BodyWorks Coconut Shae CoWash
This product is pretty similar to the As I Am product. If you like shea products for your hair you'll probably like this. For me shea is a bit heavy and caused some buildup.

EDEN BodyWorks Peppermint Tea Tree Conditioner
THIS is my go-to for my scalp eczema! This stuff is amazing. It's insanely moisturizing though and may be way too heavy for most hair. I love the minty scent and the tingling sensation on my scalp, but most of all I love that I gets rid of my crusty patches. While it is heavy, it's oil based and doesn't cause buildup. It may leave you with greasy feeling hair if you don't thoroughly rinse. With thorough rinsing, this oil based conditioner does a great job removing styling products.