My darling wife - SWMBO - gave birth to our daughter. 18 hours of labour and finally at 3.15am in the morning our lives changed.
For someone who up until that moment in time had demonstrated zero responsibility, suddenly being a father changed me in more ways than its possible to imagine. Watching her grow up and become the amazing, infuriating, smart, forgiving, hard working, supportive, creative person she is now has been the best thing I've ever achieved.
Happy birthday Squid.