I pondered a bit on how to interpret the word ‘symbol’ – is it a gesture, is it a logo, is it a physical representation (like the AIDS ribbon)? I wasn’t sure, so I put in all of them.
V for Victory
This symbol is universally known for victory, peace, and happiness (no less thanks to pretty Asian girls)
The sign was first conceived by the Belgian Minister for Justice during World War II, and etched itself into history when Winston Churchill flashed it during his wartime campaign speeches. Asians adopted it spectacularly after 1972 Winter Olympics in Sapporo, where figure skater Janet Lynn flashed it. 
The Golden Arches
I read somewhere that the Coca-Cola logo is more recognized than Mc Donalds’s logo. But that has text, so I discounted it.
It’s a beautifully proud logo, instantly recognizable. The rings and the background represent all of the countries that took part in the 1912 Olympic Games, the year the logo was introduced. 
Apple and Android
In my opinion, Apple is more recognizable as the Apple logo, as opposed to Android’s. I know people who think the latter is a logo for Google chat, Droid phones, Micromax, and recycling (can you believe that?); but I’m giving them equal weight here, so fan boys, please don’t attack me?
In the western nations, it’s recognized with a red background and needs no explanation.
In eastern and south Asian countries, it takes the form of a Hindu religious symbol from where Hitler borrowed it:
The symbol is used to invoke gods and strength, and is still widely used everyday among Hindus. In Africa, it’s used by the Ashantis, Armenians use it to symbolize light, the Chinese call it wàn, the Japanese call it manji.
I <3 this symbol. Don’t we all?
Universal. Get it, get it?
Every person I have ever known knows this one. Now Batman fans, before you jump down my throat, I am talking about people I’ve known – especially kids. Sorry, I just know more kids who know the Superman symbol than the Batman one. I often find that boys know both, while little girls know the Superman one.
The Peso sign has become so representative of the American currency that it’s called ‘dollar’, and has now become synonymous with money.
Now here’s my countdown.
The red cross is a representation of hospital and health services throughout the world.
The Handicap and Restroom symbols
These need no explanation.
According to me, the Cross is the most recognizable symbol on the planet.
I wanted to include the AIDS ribbon, but I’ve encountered at least 4 people who didn’t recognize it, so it doesn’t qualify in my head.
I also went out and asked on twitter what people think are the most recognized symbols and they all came up with the heart, the red cross, the swastika, and a star.