Many games have them, though we don't typically refer to them as bodyguards. Instead, we might think of "boss" NPCs and their "minions" or "mini-bosses". Whatever you want to call them, NPCs protecting or following other NPCs is a common sight in video games.
During his visit to New York, Pope Benedict XVI was protected by an unprecedented net of security. I was fortunate enough to be allowed on the steps of the St. Patrick Cathedral during the Mass. To get there, we had to park many blocks away, because a wide area surrounding the cathedral was blocked off and heavily guarded by police and special officers. I had to show my ticket and photo ID three times before reaching the cathedral, as well as walk through a metal detector. I'm told that the CIA did a background check on anyone who had a ticket for that area, but I can't verify that. Once on the cathedral steps, I noticed dogs, police captains and chiefs, helicopters overhead, snipers on all surrounding rooftops, secret service, and plenty of security personnel I couldn't identify. Moving between designated areas required an escort. Oh, and the Pope's bulletproof limousine was escorted by plenty of other vehicles, of course.
So what from that could be applied to game design?
- Snipers: Guards and henchmen in games are always near to the NPC they're guarding. In some cases, it might prove fun for the player to have to worry about guards out of sight or watching from afar. Such guards might be melee opponents, encouraging the player to defeat his primary target before those guards can finally reach his location. Or the player might need to select a strike position that hides him from snipers. There are countless ways to tweak this idea, but the gist is that the player must include distant objects in his awareness and cannot avoid being flanked during combat.
- Safe Zones: Security might involve a buffer zone between light security and maximum security. The scope or even existence of such buffer zones might be dependent upon player actions and success/failure. Buffer zones can be empty, blockaded areas or simply involve restricted access. If security personnel look like civilians, or otherwise harmless, then even a thick crowd be a difficult place to hide.
- Animals: Sometimes, dogs are the smart ones; even sheep. Animals often have sensitivities beyond ours (smell, vision, electrical signatures, infrared, etc.), so they can be a useful dynamic in games. It could be fun to make players worry about detection beyond visibility or noise. And we can't read animal expressions as well as our own, so great tension can be created by an animal's stare ("Is it just passing by? Or does it detect danger?").
- Choppers and surveillance: Players might have to worry about danger beyond the immediate. That a player has escaped might not mean that danger has passed, if his escape was tracked and his location is known. Surprises are fun. Allow the player to think he's home-free, then pounce on him with a sting operation. Or make him worry about whether or not he is being watched as he makes his way to the headquarters of his faction or some secret location.
- Hold the Line: Of course, players are not always on offense. With the improved collision detection of modern games comes the possibility of the player participating in a blockade. Players can act as covert guards and snipers, thereby challenged to sniff out danger before it reveals itself. Players can act as drivers and escorts, thereby challenged to adjust escape routes in reaction to dynamic circumstances.