In British English, we are starting to use more Americanised words more frequently in speech. The most popular, that I can think of off the top of my head, being 'awesome'. There are also words going around college at the moment such as 'bare'. This is used to mean sort of 'very', 'a lot of' and can be used when responding to someone to exclaim your disbelief. For example: 'That party was pretty awesome' response 'bare!' or 'That girl has bare hobbies' To be honest, I wouldn't recommend you using this - I don't use it myself because, to me, it just sounds ridiculous! Until it catches on big time that is....

Overall, the most used word is the verb "to be" and all it's other forms. This is the same in basically every language though. For slang, which I'm guessing is what you mean, I agree with TheAngelicRose, it is definitely the word "like". People use it in practically almost every spoken sentence, though it is not often written. Kids, especially teenagers, generally use it more than adults.

The most current word used in English is the word "like". Example: "I'm like, going to like, go to the mall after school." or "I'm like, not going to do that if i dont want to."

Here's the answer: http://www.world-english.org/english500.htm