What's your favorite sound effect?

This is a question I really enjoy asking people in and out of the industry, I always get a really good conversation out of it (okay maybe not always, sometimes I get weird looks). My favorite, for some reason, is the Boing Sound Effect. What's your favorite?

Mine is that 'ftup' sound you hear when you make a headshot in online games like CoD

My favourite would probably be the COD 5 headshot sound. There was just something about it that makes a headshot that little bit better - https://www.youtube.com/watch?v=l9GIIYTc7HM

Another fav of mine would be the needler from Halo 3 - https://www.youtube.com/watch?v=16LAohqD8jw This is from Halo 2 but its the same sound

Maybe not exactly a sound-effect, it's a dialogue piece that plays at the start of a number of missions in many Command and Conquer games;

'Establishing battlefield control, stand by.' 
https://www.youtube.com/watch?v=hThKfLp8gjE

A small touch - but it did add to the effect that 'You are a commander, commanding your forces through an interface to relay orders to your forces' - coupled with the way units spoke to you as a supervising officer with things like 'Sir' or 'I'm on it' or 'Awaiting orders' - it made the games a lot better in my eyes; this is mostly evident in Command and Conquer: Tiberian Sun, more so than other Command and Conquer titles.