My biceps are really activated by all types of pullups. I find that close grip chins and opposing grip pullups leave my biceps and forearms completely thrashed, and I've built some pretty good bicep size while putting an emphasis on pullups of every kind.
Current PRs at 242, raw w/ wraps- 525, 355, 605, 1485
Roboro tui, perimo vester adversarius
(Build yourself, destroy your enemy)