I've watched deer at both Farnborough and Fairoaks; also lots of foxes.
When I was at Glasgow, there was a large hare which used to sit at the edge of the apron near the tower. It would wait until a Trident taxyed out and run across to the edge of the runway to watch it take off. It did this several times as there were usually 3 Trident services which departed Glasgow between 0800 and 0830 on weekdays.