For me it's flight sims. Thought naval sims would be boring until I found a copy of Harpoon, then I sat there playing it till my eyes bled. After that was DW, now SH3. Glad to see the DW community still thriving. It's almost a work of art in its own right. I feel a hint of the long-dead Harpoon 4 when I play it (DW, that is).
Anyways, what the heck would a game be without mods?