Software with Engine Export

DragonBones was one of the first 2D skeletal animation tools, and for years the free alternative to Spine, with runtimes for the major engines and an export format several of them read directly. Development stopped some years ago, but the editor still runs and the runtimes are still around.

LDtk is a level editor with auto-tiling rules, entity definitions and a clean JSON format with loaders for most engines.

Spine animates 2D artwork by rigging it to a skeleton rather than drawing every frame, and ships runtimes for most engines so the animation plays back as bones rather than as a sprite sheet. Used with pixel art it needs care - rotation and scaling fight the pixel grid - but for characters with a lot of motion it is far less work than hand-pixelling each frame.

Tiled is a flexible tilemap editor supporting orthogonal, isometric and hexagonal maps, with importers for most engines.