What are only necessary processes (minimal set) for OS X work?
Try something like launchctl unload /System/Library/LaunchAgents/com.apple.notificationcenterui.plist and see what stops working. launchctl unload doesn't make any permanent changes, so the plist is loaded again when you log out and back in.

Some processes that might be disabled if you are trying to simplify the UI:


Dock: Also disables Mission Control, Launchpad, Dashboard, full screen windows, the application switcher, and the Notification Center sidebar, and makes desktop backgrounds gray.
Finder: Also removes the window of the desktop. Doesn't affect Quick Look or file dialogs.
mds and mdworker: Disables Spotlight indexing and makes the Spotlight menu, mdfind, mdls, and for example searching in Finder and Mail stop working.
NotificationCenter: Disables notifications and removes the Notification Center icon and sidebar.
pbs: Removes services from the Apple menu, context menus, and the keyboard preference pane.
SystemUIServer: Removes menu extras and the Spotlight menu but not status menus or the Notification Center icon.


This concatenates the man pages of processes that have man pages:

MANPAGER='col -bx' man -a $(ps -eco comm= | grep -v -e ^- -e ' ' | sort -u) &gt; /tmp/man.txt