So, Eidolons.

[Arbane the Terrible]

So, who's made a Summoner? What did you get for an Eidolon, what did they do, and how have they worked out?

[GnomePaladin]

I made a master summoner and ignored my eidolon 99% of the time.

[DBlue]

I recently did a summoner for an 11th level one shot. I don't have the sheet with me, so I might be off in a specific or two.

Half-Elf, favored class bonus to evolution points. Arcane heritage to get himself a familiar, improved familiar and muleback cords so he could be carried around. Didn't actually end up using that trick. Superior summoning, and predecessors. Everything else went to extra evolution.

Eidolon was a quadruped with a bite, four claws, energy attack(acid), maxed out improved natural armor, pounce, trip, rend, and large size. He also sported a cloak of resistance, amulet of mighty fists(acid, keen), and a strength item. Feats were power attack, combat reflexes, and improved natural attack(claw). Or was it weapon focus(claw)?

So, how was it? Absurd. The eidolon would pounce something, bite it, get a free trip attempt(usually successful), claw like a mad cat, and then rend. If everything hit, and it usually hit(with the exception of a lich), damage was between 130-150. The first unlucky recipient was a yeti who went down to -104 hp.

By contrast, with the improved natural armor evolutions and mage armor up, enemies needed to break the mid thirties to hit the eidolon's AC. Which only happened once, for a rather weak hit.

The dungeon was fire themed, and we had to face a casters. Spell Resistance and fire immunity via greater evolution surge were put on the eidolon to great effect.

The eidolon did finally get frozen by a lich's touch, but before that happened, it kept the lich occupied by itself for two rounds, at which point the lich's minions were dealt with and the full party could curbstomp the lich.

[LazarX]

I've run at least one campaign session where I never summoned my Eidolon at all. It does vary depending what I feel best serve the circumstances, my flying serpent, or having standard action summons available.

[Gluttony]

Got a combat-machine that could outdo the party barbarian for 11 levels before beginning to fall into the territory of "send her in first because it doesn't matter if she dies". And even after that point she was still quite useful, just not as useful as the raging, greatsword-wielding powerhouse.

Biped eidolon, 4 claw attacks and a bite, all of which were doing fire elemental damage on hit (we were in an area with a lot of monsters vulnerable to it) and all of which had 10ft reach. Also she got unlimited natural flight at 8th level (would have been 7th, but I dipped), which was a plus at lower levels (and VERY useful combined with Greater Invisibility + reach).

[The Henchcook]

I made an eidolon that was free of it's summoner, using Hero Lab, gave it levels in sorcerer.

[ShadowcatX]

Eidolons are stupidly powerful.

I've currently got a 4 armed monstrosity wielding short swords in one of the pbp games I'm in. Haven't had cause to use him yet, almost afraid to because the majority of the group is not really optimized and he'll steal all the thunder.