I think my personal favourite right now (until I've watched it all again!) would have to be S1 ep 6. I like the way that Martin overcomes his haemophobia in times of emergency (of course he always come through in the end, despite his "blood thing") I also like his relationship with Peter Cronk. They are both very similar characters and I could actually see Baby Ellingham growing up to be a lot like Peter.
The kiss in the car is lovely... until he goes and puts his size 11's (does anyone know Martin Clunes shoe size I'm just guessing!) right in it. And the sad thing is, he really doesn't have a clue about what he's done wrong.
I also enjoyed (if that's the right word) S2 ep 6 when the Docs parents showed up. It helped explain the way he is and it was a really, really sad scene when his wicked mother told him that he was just an inconvenience that had got in the way all these years. I so wanted to punch her lights out
Anyway, I've waffled enough! Thanks for indulging me!
I'd rather you didn't as it might ruin my plot but if anyone wants to PM me their suggestion for the murderer and their reason, I can let everyone know after I've finished Rocky Road who was right.