As it happens I have a whole list of them to hand right here:

You know, I think it is important you know, because I've been thinking it recently... You are one of the best friends in the world, and one of the nicest people, and I'm so lucky to have you. =)

At first I thought this would be a hard question, but then I realised, at my age, being unable to make new memories would be a pretty crippling affliction. Not to mention that I have photographs of past events, so while I might not remember them I could still look back on them, or even re-learn them from talking to people I know.