Community Creations
Polybar System Controllers
The Polybar System is a line of custom-made 3D printed controllers. Multiple controller sizes are available, there is plenty of documentation, and the project is open source!
I have spoken many times with the creator, roadsidebomb. He has a splendid positive personality and some real talent when it comes to engineering products. Everything I have seen of the Polybar System is a spectacular product. Superb build quality, precise buttons, fully featured, and a larger community.
If you are considering a RIFFSTICK but are not 100% set on it, I strongly recommend checking out roadsidebomb's store, threepieces.net
If you are outside of the US, there are multiple international stores. Join the Polybar Discord server to learn more about this awesome project.
Hammer-On Guitars
The best of the best. The most refined, most customizable, made to order, TOP TIER quality guitars!
I have heard many people proudly share Hammer-On guitar products, and Cameron deserves a showcase here. Take a look at the website, hammeronguitars.com, and peer into the shop. Everything is smart, laid out clearly, and the guitar customizer really shines! An amazing piece of web technology and the customization options are prominent and proud. The gallery is beautiful, definitely spend some time to view those creations.
HobbyCNC
HobbyCNC was the first store I ever bought guitar parts from. They inspired in me that controllers could be better than they used to be.
HobbyCNC's top product is fret PCB upgrades for original Guitar Hero and Rock Band controllers. If you have a guitar around that you want nicer fret buttons on, this is the best affordable option in my opinion. There are boards on the site (hobbycnc.com) for 17 guitar controllers, as well as some printed frets and a few other minor upgrades.
Prices are good, shipping is quick, good customer support to answer questions, just generally a good seller. Check them out.
760 Creations
760 Creations is a notable custom guitar creator. 760 hosts a simple & clean store of modded guitar parts, as well as fully custom modded guitars. I recommend reading through the about page to get the whole story of JB's creations. There are some premium products here, especially if you want to upgrade your existing Guitar Hero or Rock Band guitar.