What are the best Room Accustic Treaments members have found?

I  am looking into adding some room acoustic treatments to my room.  I am just looking for advice on some simple room treatments that fellow members found worthy of purchase. 
Primacoustic out of Canada is the real deal. As a division of Radial Engineering it's the same product that is used in professional recording studios. They have also standardized on colors, shapes, sizes and thicknesses so they can mass produce keeping prices low and product available for immediate delivery.

I believe also unique to Primacoustic is a paintable or printable panel. You can match or accent room color or have images reproduced by commercial printers using a big flatbed inkjet printer. 

I agree with the other poster about panel thickness and the laws of physics. A 2" thick engineered fiberglass panel is going to absorb effectivly down to about 100 Hz. The absorption of a 1" thick panel will not... A 1" thick panel works best as a scatter block on the live wall of a listening room (in an Abbey Roads style recording studio.) In a live wall - dead wall panel arrangement the speakers are on the dead wall. The scatter blocks on the live wall are a way to absorb excessive tweeter energy. In the live wall - dead wall arrangement the 2" thick panels are concentrated in the front half or 2/3 forward end of the room.

For control of standing waves typical to most rooms you'll need bass traps. Primacoustic has these as well and reccomended corner placement of the traps for best effect. The surface are of the traps should be calculated as part of the total treatment as discussed below.

There is such a thing as perfect placement. But the single biggest factor is having enough treatment to achieve your acoustic goals. This means having somewhere between 12% and 25% of the total surface area of the walls treated (not ceiling or floor surface area but walls only though paneling can be mounted on the ceiling if wall placement is not possible) depending on how "hard" or reflective your room is. Again, perfect placement is great but having enough treatment is the key and will get you 90% of the way to your goal. And that is good news because sometimes windows, doors and partner acceptance factors get in the way of perfect placement.

The nice thing about Primacoustic is that it's scaleable so that you can dial in your room. For instance, 15% not enough? Take it to 20%... Primacoustic reccomends changing  treatment in 5% increments as you'll unlikey hear smaller increments. (The tipping point is 5% with the big tipping point at 10%.) This way you can dial in your room the way you dial in your equipment rig with cables and amps.

Good luck with your acoustic goals.
David, It all depends on your room and the type of speakers you have.
For primary reflections over 200 Hz acoustic tiles work great and are dirt cheap.  https://www.parts-express.com/sonic-barrier-fwp122-studio-acoustic-foam-wedge-panel-12-x-12-x-2-black-12-pack--260-547
You can find your primary reflection points using the mirror method then place these tiles at those points. Your image will solidify.
Dealing with bass is far more complicated. The best way is to use multiple subwoofers. 
It depends what you want...
I worked with vicoustic and submitted a project to them, they came back with 3d renderings and room modes analysis and treatment suggestions.
I believe other companies offer similar services.
I used diffusers and absobers, mainly on reflective points and it brought a sense of ease to the music. I didn't go all the way because I didn't want to turn my living room into a mastering studio.
If you want something even more aesthetic, I would look at artnovion.
They have some good looking products.
Others mentionned GIK, it's also good.
ieales516 posts12-05-2019 2:04am" Books, shelves, art & carpets.

But then, I spent a few decades in sound studios, so I'm probably odd man out here. "

This must be basic. No audiophile should ever put up big pictures with reflecting glass-fronts. We need to be aware of the impact a leather sofa has in the room versus a velour sofa or chair. Know that real paintings made on canvas are wery efficient diffractors and will eat flutter-echo. Decorative wooden blinds are actually adjustable diffractors and will calm down big windows or mybe a wall. Avoid naked corners, try to brake them up with something. I have a big plastic tree in one of mine, next to a classic painting with a matching motive. Females looks at this and give me an appreciative look. If they only knew..

One thing I can say without fear of contradiction that does not (rpt not) work is SONEX foam panels. You know what I’m talking about, those sculpted dark gray open cell foam 2x2 panels that are ubiquitous in control rooms and recording studios. SONEX foam and similar products, even foam filled chairs like the IKEA POANG chair, have to be one of the worst sounding materials ever foisted on naive and gullible audiophiles. Even a little bit in the room makes the sound unnatural, phasey and wooly.