D'Addario are probably the best known manufacturer of guitar accessories, formerly known as Planet Waves, they've been around for years and have always had very high standards.
D'Addario guitar strings are excellent quality, and used by huge numbers of professional and gigging musicians, often along with their trusted guitar cables and even d'Addario plectrums!
Nowadays they have over 1000 different products, with new and innovative gear coming out all the time, be sure to use d'Addario guitar accessories all the time.