I'll agree with Veronica on Prison Break. Far and away the least interesting storyline in the series. And Sheri Palmler could have died a year sooner in my opinion.
I loved watching Dan kill The Captain in season 3 of Deadwood. I litterly went "yeah, bitch!"
Also liked it when Jeremiah killed Sims in season 2 of Jeremiah.
Even though it was a lame death, and at the end of the damn show. I was happy to see Keller go on Oz.