I was thinking about this... I've built our family's financial system (it started as a simple budgeting tool, but now it tracks everything), a Mac app to create and edit videos, quite a few developer tools for personal use, a bunch of apps for my kids, some games, and so forth.
All of these already have plenty of commercial offerings in the market, and some have open-source alternatives, but the level of personalization I get by building them myself beats any argument (IMHO)!
Interested to see what others are doing. :)
PS: I've been writing software for 8 years (5 of them professionally).