That’s a tough one. I think that so far, my favourite is the season six finale, Help Me that aired May 17th, 2010. Overall the episode was very different from many of the cookie cutter plots of the series, focusing a lot on House wrestling with his personal demons and coming to terms with his disability. I think the episode worked on a very personal level exploring a very vulnerable House. It is also one of the few occasions where House is powerless to help his patient despite his best efforts. It all makes for unique drama.
On the technical note, the episode also looked quite different from others, based on their use of a new DSLR camera with a shallow depth of field, making it look visually interesting as well.
As it turns out I have not. I slowly weaned off of television a few years ago and rarely watch anything besides occasionally checking the news or some big sporting event. The only medical show I have followed is House, MD. That is something I am considering giving up as well considering the last few episodes and the finale were poorly executed.