Using omxplayer as this has very good hardware support for playing mp4 files on a pi.

apt-get install omxplayer

Create a startup script that implements a looping playlist (note that items can be temporarily switched off/on by sommenting them out with a #hash character).

/home/pi/start.sh

#!/bin/bash
while :
do
#omxplayer TheyLiveSunglasses.mp4
omxplayer -b scanner.playlist.mp4
omxplayer -b they_live_playlist.mp4
omxplayer -b BladeRunnerEnhance.mp4
#omxplayer -b computationalvandalism.mp4
#omxplayer -b randomwalk2.mp4
done

Add start.sh to the /home/pi/.profile file...

# ~/.profile: executed by the command interpreter for login shells.
# This file is not read by bash(1), if ~/.bash_profile or ~/.bash_login
# exists.
# see /usr/share/doc/bash/examples/startup-files for examples.
# the files are located in the bash-doc package.

# the default umask is set in /etc/profile; for setting the umask
# for ssh logins, install and configure the libpam-umask package.
#umask 022

# if running bash
if [ -n "$BASH_VERSION" ]; then
    # include .bashrc if it exists
        if [ -f "$HOME/.bashrc" ]; then
       . "$HOME/.bashrc"
           fi
           fi

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
    PATH="$HOME/bin:$PATH"
    fi

# ADD THESE LINES...
clear
bash start.sh

Auto-login (with shell)

Wheezy

Edit the system /etc/inittab file to automatically login on startup (Comment out the first line, and add the second to replace it):

#1:2345:respawn:/sbin/getty 115200 tty1
1:2345:respawn:/bin/login -f pi tty1 </dev/tty1 >/dev/tty1 2>&1

Jessie (and Jessie Lite)

Use sudo raspi-config to change to boot options to Shell/autologin.

Start up job with cron

From Julien Deswaef's blog: http://w.xuv.be/projects/raspi_video_loop

To get the video to play as soon as the RasPi starts, I choosed to use Cron instead of init.d scripts. It's easier to set up and it works as expected. Here's how to set it up:

# create a crontab file
touch cronfile
# edit crontab file
crontab -e cronfile

Copy (and adapt) this line in your crontab file and save:

@reboot /path/to/your/script/./hello_video.bin /path/to/your/video/file/big_brother.h264

and restart the RasPi

sudo reboot

(As confirmed by Wendy Van Wynsberghe) this process can be done for the root user to make a script that happens (as root) when the machine starts up (no login required).