Safari Show All Tabs pinch
If you pinch (zoom) out in Safari 6.x, you can view your tabs as large thumbnails and swipe between them. It’s known under the thrilling feature title of Show All Tabs (under the View menu, or ⌘-⇧-4).

The current Safari tab zooms out to get a little smaller, and any neighboring tabs are shown on either side. I bet this is inspired by how Mobile Safari displays pages on iPhone under iOS 6 (Safari’s tab UI is a bit different in iOS 7).