In Halo the sentinels are flying machines that attack with laser-like weapons,
In Half-life the sentile is a machine gun,
Im sure in at least a few games out there besides Halo where there is an enemy(s) known as the Sentinel. If I wasn't so lazy I could probably find more examples via google (holy shit 7,500,000 links!) As you can see there is no true definiton for sentinel.
A huge robot with an array of weaponry ranging from frying pans to lasers. Most of his moves have almost no start up time and zero hangtime with the application of an advanced technique known as fast fly.
With the acquisition of unfly mode, be prepared to be perpetually stomped, frying panned, laser beamed and hyper sentinel forced. One mistake on sentinel will cost you 80% of your life. A huge robot that is feared by scrubs.
"Damn he's using sentinel that guy's so cheap!"
2. The robotic, human hunting villians from The Matrix trilogy, also referred to as "Squiddies"
3. A horribly overpowered yet badass character in Capcom's modern classic, MVC2, or Marvel VS Capcom 2: New Age of Heroes
2. In the third Matrix film, there's an awesome scene where 250,000 Sentinels are invading Zion
3. Some of the world's best Sentinel players are from Seattle (Northwest Pride!)