The QuickTime Player Applescript Dictionary reveals that the player can indeed play movies at full-screen, so you don't have to get QuickTime Pro for just that. Here's a program that lets you do it from the command-line.
#!/usr/bin/perl
use warnings;
use strict;
use File::Spec;
my $movie = shift || die "usage: $0 movie\n";
my $path = File::Spec->rel2abs($movie);
my $script = <
exec '/usr/bin/osascript', '-e', $script;
die "can't exec osascript: $?";
