IE 6, 7, 8, 9, 10 and 11. Microsoft preventing you from running the current version of their browser unless you run the current crazy incarnation of Windows is evil. IE 10 generally displays things the way other browsers do and would otherwise not make the list, but the fact that I have to use Win8 to use it puts it back on the list.
Currently, SMF because building the search index is going to take over a week and requires me to supply the admin password every 40 minutes. I could probably rip the PHP code out to do this and have it running separately as a background process, but I think the chances of getting it wrong and ending up with a useless index are high. Incidentally, it looks like we're in the top 20 SMF forums in the world based on post numbers.
Anything my dad is using because he refuses to remember what he did last time or even read the text and buttons on the screen in front of him and regularly expects me to stop whatever I'm doing to help him.