This Applescript displays the time and date in a Growl pane, with the icon of a clock. Setting Quicksilver to run this Applescript with a trigger means you can display the time & date whenever you like without having it displayed in the Menu Bar.
tell application "System Events"
set timedate to do shell script "date '+Date: %d/%m/%y%nTime: %H:%M'"
tell application "GrowlHelperApp"
set the allNotificationsList to {"Time & Date"}
set the enabledNotificationsList to {"Time & Date"}
register as application "Time & Date" all notifications allNotificationsList default notifications enabledNotificationsList
notify with name "Time & Date" title timedate description "" application name "Time & Date" image from location "/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/Clock.icns"
end tell
end tell