The 30 Days of Torchwood meme:
Day 10: A Scene that Made You Smile
The arrival of Martha in 2x06, "Reset".

See, I'm a Martha lover. She's bright and strong and beautiful, and just lights up the screen - or, in this case, the Torchwood hub.
I loved her interaction with all the characters. Teasing Gwen about how desirable they both think Jack is. Getting Ianto to talk about what Jack's like in bed - now, that is a minor miracle, since Ianto is usually so reticent and closeted. Most of all I loved her interaction with Jack, a conversation full of unspoken memories of the man they both love, the Doctor.
I loved the way Martha made Jack smile - and vice versa.
And consequently, made me smile, too.