I'm wondering which artifacts would you value useful enough to invade a crap planet just to extract them?

Storage warehouses. Credits can be made in-game, GP you cannot. So I wouldn't mind spending a few billion to take the planet and abandon it for 5GP.

mission reward artifacts (a player only has limited amounts and anything additional would be nice. (of course the artifact should be good too)

mission artis, Medal artis and some of the rarer npc drops

I invade the crap planets to steal those, and then just leave it entirely undefended. Most low-ish rank players will take the planet back so no need to abandon~

Storage structures are always worth it, as even if you abandon the planet, you're still ahead on GP. Most GP structures this is true for, with the possible exception of Weather Conrollers.

I always invade if I find a planet with an Omnibase (got 4 of them now ), and Crimson Bases are still worth it, even if not as efficient. I haven't seen any yet, but I'd take any planet with a medal structure - the cloak one in particular.

Other structures worth invading for are Drannik Databanks, Interphasic Hoveroids, Lithovoric Extractors, Meta-Tuned Jammers, Ergo-Sphere Filters, +24 structures, other stuff I can't think of.

There's other stuff that would sway me to invade, but I wouldn't take a world for just one of them - if there was a pile of such things on a planet, I might take it. That includes stuff like Hydro Meliorators, Adaptive Spires, Mylarai Strip Mines, Zolazin Analyzers, unextractable building upgrades, NPC drops and badge buildings.

the day after the medals came out, I crit-hacked a planet with a temple of reflection

I was very happy with that planet, stole a Permafrost, an intraphasic hoveroid and the temple and I didn't even get disabled for it =D and the best part, they stole the planet back I'd extracted all the artifacts

Niiice! That's the way to do it - strip everything of value, raze the defenses, let them steal it back.

Found a planet with a stealth screen and a signal restrainer. Planet had a whopping 0 cloak

I now own 3 signal restrainers

Was that the one I stole from HipHobbit?

Nope. It was a crappy planet stolen from a low rank who luckily took it back.

when i was a lower rank with cheap cost to take your planet and GP to toss it I took mission and GP artys.

Now with it costing much more to steal a planet I fined my self just giving most to legion mates . I dont think I would take it unless it had a storage mod on it. Omi base are the only things I take now, unless is full of mission artys. then i may take it but it would have to be like 6+.

I usually don't care for mission artis. GP ones catch my eye though as do some limited addition ones. It just depends on their production/space ratio for me and what production I need increased.

I made a list of structures I'd go for, even if the planet is not great (but not too bad, obviously):

Intraphasic Hoveroids
Extracted Lithovoric Stem
Warehouses
Omnibases

Lith stem is what brought on this thread, I saw one on a planet and I thought, wow that things cool, and took the planet.....Although it could have been because it's a 17x Irradiated.....either way it made me wonder which artis were worth stealing a planet for

Well, 17x Irradiated planets are good enough to steal as s, Stem's are bonuses

u cant extract +24, just in case anyone is taking note