Multiple menu item selection
Hello there!
Every so often you'd like to select several menu items and get slightly annoyed that the menu keeps closing with every click. Think of showing a bunch of email attributes (From, Subject, When, Status) in Tracker for example.
How about the possibility to do it all in one go: left clicking an item shows the current behaviour, right clicking sends the BMessage of the menu item but keeps the menu open. So you'll see any changes live, not only after the menu is closed.
Thanks Haiku-kas!

Comments
Multiple menu item selection
Yeh that's one of my favourite features from the old acorn risc-os machines that were in every primary school 12 years ago in the UK.
Lean and mean
In the case you mentioned, shouldn't that menu really be a window with checkboxes? I always cringe when I hear of "unnecessary" functionality being added to the lean and mean OS.