Hotcorner emulates Gnome 3 hot corners by switching your computer to task view whenever the mouse is moved to the left corner.
The app is only around 60 KB, and you won't even know it's running. That's almost a negative because, well you don't know it's running. But just move your mouse to towards your top left corner, and there's task view. Check out the screenshot below.
The only downside to having nothing running is a lack of options. While simple, I would prefer widening the corner area some to open it easier. Sometimes you have to get the mouse right into the very corner. A push of the space bar or a left click of the mouse closes it, but some people might want to customize that, for example, maybe it opens in the corner and closes when you exit the corner. Finally, while the app is portable you'll want to unzip it somewhere you can remember to run it from. An option to start with Windows is also needed and while it can be done, some might not know how.
That said, it doesn't get any simpler than this, and Linux users will appreciate it.