Opera Extension 1 [ LIST ]

Slim Scrollbar

Slim Scrollbar  replace default scroll bars with two simple auto-hide bars. These bars are visible only when you scroll the page. So you obtain more space, useful especially for small screens.

Snap Links‎
Hold the left mouse button to select multiple links by drawing a selection rectangle around them, releasing the button will open them in background tabs.
Shortcuts:
-Hold the Ctrl or Alt key to open the links in a Stack.

To-Read sites

This extension allows you to easily add a site you want to visit later to convenient list.
How to use it:
If you are on page that you want to visit later, click on To-Read sites button and press "add".

similar to :
Readability Redux for Chrome
Readability, Pocket (formerly Read It Later) for Firefox