Half-Life 2 @ Shack
... it can't fit under the rocks so it begins to poke around sniffing and grunting looking for alternate entrances, as its wrapping around the back Gordon makes a break for it and creates some distance between himself and his pursuer. However once crabby-spider-bull spots Gordon that distance closes quickly before getting distracted by another group of humans accompanied by an armored vehicle. The group of course panics and piles back into the vehicle only to have crabby-spider-bull start ramming their vehicle in an attempt to push it over a nearby ledge. They call in reinforcements however and Gordon can see the 8-foot menace getting gunned down by an airship as he makes his escape. [snip]
Yes, crabby-spider-bull. I came up with that one myself. Also the secret to life is... HWM.