Obviously I don't know your colleague, but one of my retiring colleagues had some interests that were in her repetoire of general chit chat, her son, her dog, and cross stitch. One of my other colleagues at her leaving do did a very funny speech (without being a comedian) about how much we will all miss her son (and recounted some antics/tales) her dog (ditto) and her cross stitch. She absolutely loved it, obviously this was concluded with a BUT we will always remember (postive traits about them and what they brought to the team) all either small but lovely things or major achievements contributions. Good Luck