
I am here to sing the praises specifically of their Love in an Elevator series. This series follows Spike though various sexcapes that occur in elevators with the various characters of BtVS/AtS. At this point in time he's gotten stuck with Gunn, Wesley, Angelus, Ripper, Illyria and Gwen.
(I'm having a blast reading Reconstructing Evil and the now completed Trials too.)