Number 1:

An easy one to start with. The ring collect sound from Sonic The Hedgehog has remained unchanged for some 17 years (unless you count the 8-bit sequels).

 
Above: Could have had the jump sound. Or the spin. Or the shield. Or the...

Number 2:

Poor Pac-Man. Sure, we could have used the 'waka waka waka' noise, but the iconic 'death' sound effect is more succinct. At least you can bring him back to life with another coin.

Above: Pac-Man will never get old. Makes us want to play it

Number 3:

Another sound that's remained unchanged for aeons is the 'you solved something' sound effect from the Legend of Zelda. This one was taken from the Wind Waker, but they're pretty interchangeable.

 
Above: We keep finding GR Matt playing this sound effect over and over

Number 4:

This cunning device used to 'increase tension'. Or, as we'd call it today, 'cover the obscenely long loading times between rooms'. Still, very well done.

Above: How much of our lives have we lost to these doors?

Number 5:

Any Call of Duty 4: Modern Warfare player will know the terror of this sound as a grenade lands right by you. "Throw it back! Throw it back! Thr..." BOOOM!

Above: A one-handed grenade catch may look cool, but really...

Number 6:

You found a secret! This sound in Tomb Raider made us feel so clever in 1996. Shame it cut in and stopped whatever atmosperic music was happening in the background. Still... clever, clever us.

 
Above: The secret this sound was taken from is off to the right here