A look at menu icons

What’s the best icon for revealing (or opening) a menu? I think the grid and “three lines icons” are good candidates. I also like the idea of using an Unicode symbol. For example, there’s a three lines symbol (≡) and plenty of downwards arrows (↓ or ⇩ or ▾ or ▼). I don’t agree with using a plus sign; this should be reserved for “adding” actions.