What are some of the best editors to use today?

I've worked in plenty of editors, from the 3D to the 2D, proper engines/toolsets and simple level editors. My question to the community at large here is what are some of the best engines to make levels in that seem appealing to many people? I'm going to be working on a project over the next 6 months and I am flexible with engine so I would be interested in hearing some of the more competitive engines to construct a level or level(s) in in the future.