SH3 DVD +
GWX SuperMod is one sweet game. No DRM (not even SecureROM), fully patched out of the box. You might run into some problems running it on Windows 7 though, I did. But it's only $10.
I've never been too happy with Silent Hunter IV though, mostly since I didn't like the fleet boats. The U-boat Missions thing still feels like an afterthought.