What is a Good Garry's Mod Server Host?

I recommend www.hexanenetworks.com . It has got a very nice support, fast addon downloading and a niceinfrastructure.

Try and use Crident Networks as it is really reliable.

Hexane networks, they have good support and good servers imo

I could recommend crident since how they work with not paying for slots i am pretty sure this was mentioned before

I'd recommend Crident, they have good response times, come with a mod manager, lag-less servers and much more!

You should definitely use Crident.
If you do end up using crident, use code "BILLY" for a 25% discount.

Hexane Networks was good. I was Developer on a friends server hosted by them and they had stable servers and good support.

GMCHosting if you have the money to spend. It's really good and their custom DDOS protection makes them stand out from the rest.