Caveat: I got all of these examples from somewhere over the years and collected them in a folder. If you recognize your work let me know – I want to give you credit!
Vertical Drop Down
Basically styled, this dropdown is lightweight and supports nested submenus.
View Demo I like this menu. It is very minimalist, but the CSS could be jazzed up if you need more flair. It is nice and clean though and will work everywhere.
Clean Drop Navigation
When clicked, the submenus drop down from a rounded button. Though I have the buttons on a contrasting background, you could make them both the same for a cleaner look, or add a gradient for a more 3-d feel.
Graphic Background Menu
An awesome way to use a custom background and break out of the horizontal menu look.
Garage Door Sliding Menu
On hover the images for each button slide up to reveal text behind the button. I think this one is unusual as well and add some interest to a page.
YouTube Style Buttons
Buttons that are unobtrusive, but when hovered over seem to pop up. I need to work on coding a solution for the dropdowns for these buttons.