vBulletin mainly, but also can still find my way around MyBB, IPB (1.3.x - stopped using it when it wait paid), phpBB, and starting to get the hang of (albeit slowly) SMF.
If it wasn't for the fact that my server is too up to date with php and mysql, I would have reverted back to vB2.3.x a couple of years ago because it does what I needed it to do at the time without too much fluff involved (this was when I made the mistake of upgrading to vB 3.7 and instantly hated it)