Well, if you're looking for something broken, Truenamer certainly is that. Just not the way the OP wants. Seriously though, Druid is probably your best bet. As long as you take Natural Spell at level 6, there's not many ways to permanently mess up your character. Look over the Monster Manuals for an animal that appeals to you for your Animal Companion, make sure you scale your Wild Shapes so you aren't using the same ones from level 6 at level 10, and make sure you pay attention to your spells, and if you notice a spell you prepared not being used, switch it out for something else. Remember, Druids have to prepare their spells, but they know all the spells on their list, so if you come across a spell that looks cool, and it's on the Druid spell list, you can prepare it. And yeah, Greenbound Summoning is crazy good on a low level druid.

MrRigger