I can't beleive no one has mentioned this, but how about that Power in Castlevania Symphony of the Night where you would shoot this fireball thing from behind your cape? Only, if you used the power and held the UP button down, you would go invisible, shoot across the screen, then attack in the opposite direction with 3 of those fireballs. It would basically wipe out anything on the screen, except a boss, and even then it did quite a bit of damage. Speaking of which... that game had all kinds of weird stuff in it. Just things that were just cool, that really (for me) changed the way I see games as an interactive medium. MGS also did this to a smaller degree, where you had to look on the jewel case to see Merideth's call number, and pretty much the entire fight with Psycho Mantis. Oh yeah, and I just have to say this, even though it's technically not an easter egg type thing. But the fact that Bionic Commando was so badass with that bionic arm. That made the game right there.