The TV prankster was killed in a high-speed car crash in Pennsylvania last June (11), and Knoxville gave a special reading at a memorial service days later.
Knoxville also penned an online tribute in the wake of the tragedy, but has rarely spoken about his pal's death since. However, on Wednesday, he told his Twitter.com followers he had visited Dunn's resting place in Brecksville, Ohio.
Uploading a photo of the gravestone, which features an image of Dunn and was surrounded by flowers, Knoxville wrote, "We just visited Ryan's grave out in Brecksville. Was glad to see he has had many people coming by to visit."