The B757 used to be a regular visitor up until 2000, since then visits declined and there hasn't been one for more than a year. Britannia used 767s for a few charters in the early 90s but I believe they are now banned due to taxiway and parking restrictions. BA also used a Tri-Star once when there was a backlog due to fog and an A310 also visited on occasion.
More recently the largest visitor has been an RAF C-17 for training approaches.