I really, really love Agatha Christie’s Poirot. He is the one detective, besides Sherlock Holmes, that I remember reading as a kid. And re-reading years later (and continuing to read even when I would remember who had done half way through).
Peter Ustinov was the first Poirot I watched on TV; I think I might have seen The Death on the Nile (1978) a couple of thousand times, it was one of my favorite films when I was a child. But David Suchet is defenitely my favourite Poirot.