Topi Ylinen is the creator of the popular and influential Angband variant Zangband. This developed out of a previous, less developed variant that was distributed as a set of diffs at one point, by the name Angband--. This had a lot of Calvin and Hobbes uniques and did introduce some features that carried over into Zangband, such as mimic nests. It was light and fun, whereas Zangband really started to make serious changes and, while not without humor, was not so light.
Topi Ylinen has, hands down, the coolest name of any roguelike developer.