What is the best TV Tuner card to be used with MythTV?

If you don’t need analog, I really like my HDHomeRun box, it’s a network device, mine has dual tuners and is fairly easy to set up (although my particular setup is weird due to how the cable co splits out the locals randomly)
(Note, if you like my answer, please give it a Great Answer before commenting – I am trying for an award ;-) )

So you use HDHomerun with MythTV?

Yes. I have cable internet, so by FCC rules my cable provider (Comcast) must include the locals – that or it’s easer on them not to filter ;-)
I use MythTV with the HDHomeRun connected to a MythTV Backend that has a lot of storage (on HD channels an hour is 6–7GB) with the TV connected to a different Frontend machine.
It works pretty well for me. I just wish I could use a cablecard or something to get the non-local channels (even basic cable is encrypted) but that’s an issue with MythTV as a whole (because it’s not Windows Media Center, which is the only program I know of that supports those)