I love the sheer musical quality and diversity of Dark Side, the desperate rallying of The Wall and the vageuly Orwellian bits of Animals.
Time is one of my favourite songs of theirs, great beat and a great set of lyrics. Wish you Were Here is really touching, and I like the epic Shine on your Crazy Diamond and Echoes too. Hey You is also very enjoyable, and of course Another Brick in the Wall is just an all time classic. There early stuff with Barrett was interesting, if...amazingly weird (even by the standards of their later work).
Surely one of the best bands in rock history, wouldn't it be great (if unlikely) if they got back together properly (Roger Waters and all).