The Hounslow Roundabout service from Waterloo turns right at Barnes, goes round the loop, and then comes back and crosses its own path at Barnes again about 45 minutes later.
When I was last at Waterloo I noticed it was announced on the automated announcement PA as calling at "Vauxhall, Queenstown Road, Clapham …. Clapham, Queenstown Road and London Waterloo". I hadn't noticed that before, and seemingly whoever set the PA up, presumably from the working timetable, hadn't noticed it either.
There were previously several such looping services from Victoria and London Bridge which did the same, but these seem much reduced now.