Here are some recent combos I discovered. Feel free to add your own combos to this thread for discussion.
Juvenile Wyvern + Shrine to Nurgle = Great blocker and all units it blocked are corrupt
Juvenile Wyvern + Warp Light Cannon + Chillwind = Attach cannon to wyvern and you really have a great blocker, use chillwind to uncorrupt it after you attach
Har Ganeth + walking sacrifice = free card every turn
Har Ganeth + any unit with comes into play ability (eg, Night Goblins) = unlimited attachment card destruction
Har Ganeth + Caught the Scent = get rid of an opponents nasty unit
Abandoned Mine + City Gates = free card every turn
Bloodsworn + Cloud of Flies (can't take credit on this one, read on another thread)