Cheap root server providers, mostly in Germany if nothing mentioned otherwise, all with own infrastructure (no resellers) and my personal experience. Note that prices mentioned in Germany are almost all the time incl. VAT, so you might be able so save 19% on those prices.

https://www.hetzner.de/us/hosting/produktmatrix/rootserver - Hands down my favorite. Very powerful hardware for the price, very professional, good network

https://www.webtropia.com/en/ - extremly cheap, many different offers, good quality, good option if price is very important

https://www.hosteurope.de/en/Server/ - The "Root Servers" they sell are actually VMs. High price but good quality

https://www.strato-hosting.co.uk/server/dedicated/ - Belongs to Deutsche Telekom, big company, I never used their dedicated servers (the VMs are crap though)

http://www.server4you.com/dedicated-server/ - cheap, big company, quality is ok. Other brands are Serverloft, Plusserver, unmetered.com

https://www.1and1.com/server-dedicated-tariff - big company, good network, not that cheap

http://www.euserv.com/en/dedicated-server/index.php - many different offers, good support, good value

https://english.keyweb.de/products/server/dedicated-server/ - never used the dedicated servers, VMs are crap

https://www.ip-projects.de/produkte/premium-rootserver/ - no personal experience

https://contabo.de/?show=server - Small company, good offers, good support

https://www.manitu.de/root-server/ - Small company, very good support

http://www.seflow.net/dedicati/ - ITALY, small company, very cheap, good

https://www.online.net/en/dedicated-server - FRANCE, very big company, very cheap, good network

https://www.digicube.fr/index/comparatif - FRANCE, extremly cheap, network not that good

http://www.kimsufi.com/us/en/ - FRANCE and CANADA, very cheap, good quality, very good dDOS protection. Other brand of OVH is SoyouStart

https://www.leaseweb.com/bare-metal-server/all-servers - NETHERLANDS, very big company, very professional, kind of expensive, DCs in different countries