This happened about two years ago and I was so blown away I took notes and told my wife about it, so I still have the notes on my phone. My 5yo son was pretty typical for his age; always goofing around, never serious, always working some angle to negotiate treats or buying whatever thing was at the top of his list this week. Kids have a selfish worldview and that's mostly indetstandable because they haven't matured yet. So when my son asked me to go for a walk just the two of us, I immediately laughed and thought "ok, what's he going to ask for".
We start walking and I ask "what's on your mind buddy?". He said "nothing really, I just want to have some time to be with you and be peaceful and be out in nature". Wow ok, this is progress I thought. Then he said "I want you to know you're the best Dad I've ever had. You really do help me and my sister a lot and you're really very nice, even though we don't usually tell you. So I just wanted to say 'thank you for everything' and that I want to be near you always." By this point, the only reason I wasn't completely crying my eyes out is that I thought it was some kind of a joke or lead up to ask for something, this was totally out of character especially at this age. I managed to croak out something like "I'm really glad to hear that and I love you very much". Then we just enjoyed the rest of the walk.
It really felt like for a moment I was speaking to a soul who has had several lives ("you're the best dad I've ever had") and wanted to speak directly to me instead of play the role of a child. I'm so glad it happened and it's something I will never forget. Later he went right back to being the same old goofy kid that I love.