While not a complete list by any means, these are some unfamiliar name variants I could think of off the top of my head.
Generally, all forms of Arthur are too close to the original to fool anyone. The best I can think of is Artair, the Scottish form. Though you could use a Welsh/Old Brythonic name like Arthmael ("bear prince").
Morgana/Morgan le Fay is similarly difficult to obscure, since her earliest name is still Morgen.
Guinevere has many variants. Some of the more unfamiliar ones may be Guanhumara (Geoffrey of Monmouth's rendering in Latin), Wenneuereia (used by Gerald of Wales), and Findabair (the Irish cognate). Winlogee is presumably Guinevere in a carving on the archivolt of Modena Cathedral in Italy.
For Gawain, there's Gwalchmei (Welsh), Gualguanus (Geoffrey of Monmouth's rendering in Latin), and Gauvain (French). Balbhuaidh is the Irish form.
Arnive was the name of Arthur's mother in Wolfram von Eschenbach's Parzival.
Bedwyr is Bedivere's original Welsh name. Beduerus is Geoffrey of Monmouth's rendering in Latin.
Galath and Lanslod for Galahad and Lancelot.
Medraut is one of many variants of Mordred. It's also the original.
Myrddin is the Welsh name for Merlin.
In place of Camelot, there is a pretty decent list of courts Arthur had, in Welsh sources: Caerleon (his capital according to Geoffrey of Monmouth), Mynyw, Pen Rhionydd, and Celliwig/Gelliwic.