I don't think any are really "unplayable", they can be very challenging and require unusual methods to succeed or survive but that has its own charm.

I had a ton of fun with the vampire coast on ME campaign.

On vortex, i loved the elves on the islands south of southlands.

For the rogue factions, the college of pyrotechnics and the wrath of nature factions are fun to battle with. Explicitly help out one main faction and get an exclusive military alliance that is like your merc contract and then help that ai faction gain world domination.
This can be fun because ai empires can be derpy so it requires more turn-by-turn management but also if their towns get jacked hey it's not like it's your stuff lol

Vashnaar's Conquest as a rogue faction is almost unfairly good. I also agree with Dazbohnes that those are fun too. I would argue Morssileb's Howlers, Abominations, Jerrod's Errantry Army, Hung Warband are good choices too. I did a game as Stuff Snatchaz also that was fun until late game. In my opinion playing as a rogue army while you have a co-op friend play as a "normal" faction is a good time. Vashnaar's Conquest is so good because they get ridiculous garrisons for some reason that make them pretty much impregnable so you can actually take territory (hint: only take plaes with ports or trade buildings to make a little money) and you can then trade with a co-op partner. Plus their roster is just really good.

For my ME campaign, I've been playing the Xlanhuapec faction a lot. I'd carve up the entire southern Lustria conteninent between Xlanhaupec, Itza and the Sentinels of Xeti and we'd expand outwards for total domination.

I've assisted the Last Defenders take control of all the entire deserts south of the Orcish badlands and just finished wiping out the High Elves, giving Hexoatl's total control of the entire island of Ulthuan.

It's the most fun I've had in a TW campaign.

Originally posted by SK8 2 CRE8:

I've assisted the Last Defenders take control of all the entire deserts south of the Orcish badlands and just finished wiping out the High Elves, giving Hexoatl's total control of the entire island of Ulthuan.

You didn't confederate left right and center, and own all of the Southlands and Ulthuan yourself?

The lizardmen AI in my campaign (for whatever) reason were very aggressive. As the Sentinels, Itza and I took control of Lustria, Itza began sailing towards the Old World.

Hexoatl was already invading Ulthuan and almost all of the entire west coast of the southlands were in ruins for some reason when I arrived. (I think the Chaos invaders might have had something to do with it) Khemri was the only faction I had to contend with in the southlands with the help of the Last Defenders waging war.

Knights of whatever across on the desert, if you have the legendary lord for them its great, bretonnia in the desert, Deus Vult. Kinda.

Originally posted by Slav:

Knights of whatever across on the desert, if you have the legendary lord for them its great, bretonnia in the desert, Deus Vult. Kinda.

I take it you're not playing Fyrus then, because poor Fyrus can't recruit any units until its building gets to T2 :P

I really like Blood Hall Cabal or their name is something like that. They are a Dark Elf faction in Lustria, which Dark Elves are my favorite faction but there is not lot of Dark Elves outside of Dark Elf homeland area. They got nothing special going for them as they start out with a rubbish outpost and small army. However they have a good defensible position, between a mountain range and the edge of the map, so attackers only come from the North or South.

Originally posted by RorschachInk:

They got nothing special going for them as they start out with a rubbish outpost and small army.

minor factions in a nutshell :P

Originally posted by RorschachInk:

I really like Blood Hall Cabal or their name is something like that. They are a Dark Elf faction in Lustria

Blood Hall Coven, I think you'll find :P

I loved playing as the Chaos Warriors in the Vortex campaign, them in conjunction with SFO II really made me realize how much fun it can be to play as Chaos! Though it makes me realize that there are potential Legendary Lords that exist ONLY in Vortex and not in ME (Like Vardek Crom - known as Crom the Conqueror within the game).

I have had a blast playing as Karak Zorn, the red and blue dawi in the southlands. you are surronded by tomb kings, scaven, vampires, and lizardmen. It has been quite a challange to build up your montain empire and try to make contact with the northern dawi, but that is half the fun right? I have currently taken out Clan Mors, the Silver Vamps, and I am working on the Asp Queen (I forget how to spell her name Kolita??) I was fighting the lizardmen but after pushing them back into the jungle which is uninhabbitable as the dawi, I forced them into a military alliance with trade. Next I am heading north to reconnect the old trade routes and start pushing back against the greenskin hordes.

Originally posted by Chaos:

I have had a blast playing as Karak Zorn, the red and blue dawi in the southlands. you are surronded by tomb kings, scaven, vampires, and lizardmen. It has been quite a challange to build up your montain empire and try to make contact with the northern dawi, but that is half the fun right? I have currently taken out Clan Mors, the Silver Vamps, and I am working on the Asp Queen (I forget how to spell her name Kolita??) I was fighting the lizardmen but after pushing them back into the jungle which is uninhabbitable as the dawi, I forced them into a military alliance with trade. Next I am heading north to reconnect the old trade routes and start pushing back against the greenskin hordes.

I just made it north on my karak zorn playthrough, and the whole 'restoring trade routes to get technology' is broken, super dissapointed. the journey was fun, so i guess thats what counts.

Carved out a huge Empire as the southern dwarves, couldn't unlock any technology.

I don't need it, helping my technologically more advanced allies with massed great axe warriors, crossbows at the very highest experience level (they have been killing the enemy since turn 1) and not to mention grudge throwers for anything bigger.

Who needs gunpowder? Lol