All of these monsters are Super Uniques located in in Act 5.

Snapchip Shatter - Superunique Frozen Creeper located in Icy Cellar (a sub-dungeon in Ancients Way)

Frozenstein - Superunique Frozen Abyss (basically a giant Yeti) located in Frozen River (sub-dungeon in Frozen River; he's the leader of the pack guarding Anya while she's still frozen)

Doc Farren - Superunique Demon Gremlin located in The Bloody Foothills (he's about halfway through the area)

Bonesaw Breaker - Superunique Reanimated Horde located in Glacial Trail (he and his pack are basically guarding a glowing golden chest).

I found and gathered all this information from the following 2 links:
http://www.battle.net/diablo2exp/mon...runiques.shtml - Act 5 Super Uniques

http://www.battle.net/diablo2exp/maps/act5.shtml - I briefly conferred with this page to make sure I got all of the correct locations for the sub-dungeons.