When at university in Hatfield, there was a lovely little bin especially marked for 'used tickets'. As the vast majority of travellers from Hatfield were in the City for a day, this used ticket bin was generally full of all-day travelcards by around 6pm. Which meant loads of cheaper nights out...
Not forgetting the old Aldrington Halt scam - where miraculously almost a whole train load of folk used to queue at Brighton to get their tickets when getting off the west coast line, all of whom seemingly got on at Aldrington!