Pronounced "Hahv". Well, that's how I say it. Welsh pronunciation is "Haav", I think, but I'm English (moved to Wales when I was three). My old primary school headteacher had a baby called Carmel Haf, which I thought was sweet. There are two teachers at my school with the middle name Haf, too. It's an extremely popular middle name in Wales, but I think I prefer it as a first!