TLDR; Good job gearbox. Not much left to respawn for us! Zarpedon is the big deal from what’s left but now we can do very cool farming runs that probably hits all the maps!
I found someone’s list of unfarmable/unrepeatable bosses/unique enemies:
http://www.gamefaqs.com/boards/783734-borderlands-the-pre-sequel/70375564
http://oldforums.gearboxsoftware.com/showpost.php?p=5074085&postcount=3
Flame Knuckle - Nukem (first boss during Intro)
Even-More-Disgusting Tork - Flakker (from quest “All the Little Creatures”)
Rooster Booster - Oxidizer (from quest “Grinders”)
Meat Head - Meat Grinder (from quest “Rough Love” - 1st Suitor)
Drongo Bones - Fatale (from quest “Rough Love” - 2nd Suitor)
Gigantic Ice Shuggarath - Zim (from quest “Bunch of Ice Holes”)
Rabid Adams - Unique SMG (From quest “Treasures of Echo Madre“)
Boomer - Kerboom, unique grenade - (from quest “Nothing is never an option”)
Bruce - Supernova (From quest “Another Pickle”)
Power Suit Noob - Shooting Star, skins (2nd courier in quest “Red then dead”)
Zarpedon - ZX-1 (Can get this from final boss)
Zarpedon Ascendent - Bulwark, Legendary Skins
Meg - Torrent (from quest “Kill Meg”)
Tiny Destroyer - Moonlight Saga (from quest “Lab 19”)
Lazlo - Lazlo’s Freezeasy (he drops a blue version of the quest item. Don’t worry if you missed it, it sucks. From quest “In perfect Hibernation.”)
CL4P-L3k - 3DD1.E (from quest “Eradicate!”)
Infected Dahl Soldier (eghood)- Blowfly (also from quest “Eradicate!”)
And a list of farmable bosses:
http://oldforums.gearboxsoftware.com/showthread.php?t=395907
Deadlift (DROPS: Vandergraffen. LOCATION: Regolith Range, during the Story Mission)
Nel (DROPS: Skullmasher. LOCATION: Regolith Range, after the “Last Requests” quest. Video showing how to spawn him [not my video])
RedBelly (DROPS: Striker, Black Snake, heads, skins. LOCATION: Crisis Scar, Story Mission)
Felicity (DROPS: Quasar, skins. LOCATION: Titan Robot Production Plant, Story Mission)
Bosun (DROPS: Cryophobia, heads, skins. LOCATION: Pity’s Fall, Story Mission)
*RK5 (DROPS: Unconfirmed, but it would seem he can drop any Legendary. LOCATION: Outfall Pumping Station [must travel through Vorago Solitude to get there], Story Mission)
Sentinel (DROPS: ZX-1, Longnail, Black Hole, Celestial/Eridian class mods, skins. LOCATION: Eleseer, Story Mission)
Iwajira (DROPS: Thingy, skins. LOCATION: Serenity’s Waste)
X-STLK-23-2 (DROPS: Eridian class mods, skins. LOCATION: Research and Development)
Corporal Bob (DROPS: Ack Ack Oz Kit, skins. LOCATION: Hyperion Hub of Heroism. Enter and exit Jack’s Office to make him spawn)
Meg (DROPS: Torrent, skins. LOCATION: Hyperion Hub of Heroism, “Kill Meg” quest. SaveQuit after killing her to fail and retake quest, which makes her respawn)
**CL4P-L3K (DROPS: 3DD1.E. LOCATION: Veins of Helios [travel through Lunar Launching Station], “Eradicate!” quest. Only respawns if you choose to SECURE him during the quest. If you choose to DESTROY him, he will not respawn)
Eghood (DROPS: Blowfly. LOCATION: Veins of Helios, “Eradicate!” quest)
Lazlo (DROPS: Lazlo’s Freezeasy [unique version]. LOCATION: Veins of Helios, “Quarantine: Infestation” quest)
These bosses also respawn, but currently have no known drops, aside from skins for some*** (they may have extremely rare drops, or do not have a set drop);
Son of Flamey (DROPS: Skins. LOCATION: Serenity’s Waste, “Tales from Elpis” quest)
[Phuper] Phonic (DROPS: Money (ring formation). LOCATION: Serenity’s Waste. Doesn’t always spawn. You may need to zone out/in or SaveQuit to make him spawn.)
Oscar (DROPS: Skins. LOCATION: Triton Flats, behind the building with “Pop Racing” quest)
Magma Rivers (DROPS: ?. LOCATION: Triton Flats, Story Mission)
Wally Wrong (DROPS: ?. LOCATION: Triton Flats, Story Mission)
Fair Dinkum (DROPS: ?. LOCATION: Triton Flats, Story Mission)
Swagman/Outcast (DROPS: ?. LOCATION: Stanton’s Liver)
Opha Superior (DROPS: Skins. LOCATION: Eleseer, “Guardian Hunter” and “Sterwin Forever” quest)
And now we can add:
Tiny Destroyer
Boomer
Rabid Adams
Giant Shuggarath
Bruce
Rooster Booster
Even-More-Disgusting Tork
Tony Slows
Drongo Bones
Meg
CLAP-L3K
Lost Legion Powersuit Noob
Meat Head
And the differences:
Remaining unfarmables:
Zarpedon - ZX-1 (Can get this from final boss)
Zarpedon Ascendent - Bulwark, Legendary Skins
Lazlo - Lazlo’s Freezeasy
Infected Dahl Soldier (eghood)- Blowfly (also from quest “Eradicate!”)
Now farmable but wasn’t at first, or only situationally farmable:
Flame Knuckle - Nukem (first boss during Intro)
Rooster Booster - Oxidizer (from quest “Grinders”)
Boomer - Kerboom, unique grenade - (from quest “Nothing is never an option”)
Tiny Destroyer - Moonlight Saga (from quest “Lab 19”)
Rabid Adams - Unique SMG (From quest “Treasures of Echo Madre“)
Gigantic Ice Shuggarath - Zim (from quest “Bunch of Ice Holes”)
Bruce - Supernova (From quest “Another Pickle”)
Even-More-Disgusting Tork - Flakker (from quest “All the Little Creatures”)
Tony Slows
Drongo Bones - Fatale (from quest “Rough Love” - 2nd Suitor)
Meg - Torrent (from quest “Kill Meg”)
CL4P-L3k - 3DD1.E (from quest “Eradicate!”)
Power Suit Noob - Shooting Star, skins (2nd courier in quest “Red then dead”)
Meat Head - Meat Grinder (from quest “Rough Love” - 1st Suitor)
Plus what we could farm before (some dupes as it includes the situational farmables):
Deadlift (DROPS: Vandergraffen. LOCATION: Regolith Range, during the Story Mission)
Nel (DROPS: Skullmasher. LOCATION: Regolith Range, after the “Last Requests” quest. Video showing how to spawn him [not my video])
RedBelly (DROPS: Striker, Black Snake, heads, skins. LOCATION: Crisis Scar, Story Mission)
Felicity (DROPS: Quasar, skins. LOCATION: Titan Robot Production Plant, Story Mission)
Bosun (DROPS: Cryophobia, heads, skins. LOCATION: Pity’s Fall, Story Mission)
*RK5 (DROPS: Unconfirmed, but it would seem he can drop any Legendary. LOCATION: Outfall Pumping Station [must travel through Vorago Solitude to get there], Story Mission)
Sentinel (DROPS: ZX-1, Longnail, Black Hole, Celestial/Eridian class mods, skins. LOCATION: Eleseer, Story Mission)
Iwajira (DROPS: Thingy, skins. LOCATION: Serenity’s Waste)
X-STLK-23-2 (DROPS: Eridian class mods, skins. LOCATION: Research and Development)
Corporal Bob (DROPS: Ack Ack Oz Kit, skins. LOCATION: Hyperion Hub of Heroism. Enter and exit Jack’s Office to make him spawn)
Meg (DROPS: Torrent, skins. LOCATION: Hyperion Hub of Heroism, “Kill Meg” quest. SaveQuit after killing her to fail and retake quest, which makes her respawn)
**CL4P-L3K (DROPS: 3DD1.E. LOCATION: Veins of Helios [travel through Lunar Launching Station], “Eradicate!” quest. Only respawns if you choose to SECURE him during the quest. If you choose to DESTROY him, he will not respawn)
Eghood (DROPS: Blowfly. LOCATION: Veins of Helios, “Eradicate!” quest)
Lazlo (DROPS: Lazlo’s Freezeasy [unique version]. LOCATION: Veins of Helios, “Quarantine: Infestation” quest)
These bosses also respawn, but currently have no known drops, aside from skins for some* (they may have extremely rare drops, or do not have a set drop);**
Son of Flamey (DROPS: Skins. LOCATION: Serenity’s Waste, “Tales from Elpis” quest)
[Phuper] Phonic (DROPS: Money (ring formation). LOCATION: Serenity’s Waste. Doesn’t always spawn. You may need to zone out/in or SaveQuit to make him spawn.)
Oscar (DROPS: Skins. LOCATION: Triton Flats, behind the building with “Pop Racing” quest)
Magma Rivers (DROPS: ?. LOCATION: Triton Flats, Story Mission)
Wally Wrong (DROPS: ?. LOCATION: Triton Flats, Story Mission)
Fair Dinkum (DROPS: ?. LOCATION: Triton Flats, Story Mission)
Swagman/Outcast (DROPS: ?. LOCATION: Stanton’s Liver)
Opha Superior (DROPS: Skins. LOCATION: Eleseer, “Guardian Hunter” and “Sterwin Forever” quest)