Quite Legacy cards with new-ish drivers and OS [caveat?] [note] [log bug][warning]
TeraScale mobile dedicated GPUs with Intel IGPs
Very latest driver for pre-GCN hardware [overview]
EDIT: VSR can be forced on a lot of cards
EDIT2: folks on Windows Vista can get 17-months-newer drivers with minimal hacks
EDIT3: new king in town
Reliable firm confirmed milestones
10.2 - latest driver supporting everything that ever lived
14.4 - latest driver supporting fixed switching
16.1.x branch (see above) - latest driver supporting pre-GCN
17.7.1 - latest to officially support W8.1, but it can be hacked
18.9.3 - latest 32 bit driver