S03E02 - Trouble In Mind
S04E01 - Highest Castle, Deepest Grave
S05E09 - 'V' For Vashon: The Son (I know some put the trilogy into 1, I'm separating them!)
S09E19 - Blood Money Is Hard To Wash
S10E24 - Death In The Family
S11E17 - Stringer

These episodes are solidly made, especially Blood Money. Dane Clark is fantastic in this appearance.

Nancy Wilson gave an unforgettable performance in Trouble in Mind.

What all these episodes have in common is that our favorite detectives had to work at the mystery. But once they solved the puzzles, look out!

Just my 2 cents. Mr. Mike, you picked well too.