First of all, it is 'what', not 'wat'... People on 랜덤 need to use proper grammar, 또는 they can leave XD. Secondly, dude they're just letters, what the h**l have 당신 been smoking?
Since I'm nice, I'll answer anyway, given your discrepancies.
A letter I like (I have no favorites) is 'T'. It is useful in a lot of words, so I like to utilise it. XD