In no order.
Quicksand
Word on a Wing
Watch That Man
Life on Mars?
Dollar Days
1984
Starman
Changes
"Heroes"
Fantastic Voyage
Quicksand
Honourable mention: Station to Station.
How about instrumentals? My fave is Subterraneans.
EDIT: Ah crap, forgot Ashes to Ashes. This is a futile task