I am making a 3D turnbased RPG (think Dragon Age: Origins style camera), and I am looking for an engine. My current first choice is Sunburn 2.0, but I am open to alternative if they would be more suited to what I am trying to make. Ease of use is the first concern, but having decent graphics would also be nice. I have also looked at Unity and the UDK, but Sunburn looks a bit easier to work with.
Thanks,
-Ghost55

UDK and Unity are very good and popular engines, the latter is important when you need support. Both engines come with a good tool support, even when they don't seem to be easy at first, it could pay off in the long run.

I am yet to get started with game dev properly (had a few things in the way) so my opinion might not count as much as someone thats had experience, besides, I'm probably going to be asking myself the same question in a few days (want to start a project as something to do this summer).

I believe there is far more support for the id3 (quake 3 engine) than id4 (doom 3). ioquake3 is a fairly popular project maintaining the quake 3 source. There is an iodoom aswell but last I checked it seemed pretty dead, ioquake is still going. The lack of id4 support though might just be a case of id3 being around longer and still doing its job well.
If you were to use one of the id engines then they are currently GPL licensed so with some tinkering you could theoretically add any extra features you wanted to the engine.

I believe 7dfps has a listing of free game engines aswell all though they are a website orientated around first person rather than third person.
Another AAA quality option like UDK is cryengine 3 which is also available on a free non-commercial license or a royalty based commercial license for solo developers.