John Merrill became the first person to walk the entire coastline of Britain, averaging 26 miles per day with 50lbs on his back for 10 months.

BBC: Tom Brabham prepares for walk around British coastline

When asked by ABC how he planned to top the walk over Niagara Falls, Wallenda said he hopes to become the first person in the world to walk a tightrope across the Grand Canyon, in Arizona.

CNN: Daredevil completes walk across Niagara Falls

Roberts attached himself to the robotic arm and he got--he was the first person ever to be underneath the space shuttle during a space walk.

NPR: Shuttle Spacewalk Repair Mission a Success