dein.vim: As a follow up of this question, I'll add here the plugin manager made by the well-known Shougo.
According to the README, the plugin has the following dependencies:
Vim >7.4 or neovim: while keeping Vim up to date is a good thing, it may be problematic for some users that previous versions are not supported
git: which is pretty common for a package manager
rsync: which is not as common as git
The author claims that it is faster than NeoBundle. A benchmark can be found on the project's readme page.
One original concept of this plugin manager is that it does not provide any commands, but only functions: for example, to update your plugins you can't use something like
:PlugUpdate, you'll have to call:
:call dein#update(). To be honest I haven't found an explication of this design choice.
Also, someone created a plugin which provides these "missing" commands. I have no idea if this is a good idea or if this is against the main idea of the plugin manager but the author mentions it in the FAQ of the doc file.
Dein.vim supports getting plugins from Github (with a facilitated access to plugins from vimscript.org) and from local directories.
The plugin manager provides some classical features like updating and disabling the plugins. It also allows the execution of hooks at installation time.
Note that according to the FAQ, it seems you have to manually build the helptags of the plugins it installs.
An interesting point is that the author wants dein.vim to be easy to test and to maintain so the repository also contains some test scripts.
Finally, I'd say that this plugin manager seems to be designed to be lightweight and fast, which is interesting, but I think it is less user-friendly than vim-plug or Vundle, for example.
Oh, also, Shougo describes dein.vim as a "Dark powered Vim/Neovim plugin manager" if any one knows what it means, feel free to edit this answer: I'm curious ;-)