ResizePixel is a free online image editor where simplicity is essential feature. It is designed to crop, resize, flip, rotate and convert images to various formats. The service is mobile-friendly, fast and easy to use.
GifJif - Turn GIFs into masterpieces.
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.
Giphy - Search all the gifs and make your own animated gif
Ralpha Image Resizer - High-speed image batch conversion tool
GifLab - The easiest way to create GIFs on your iOS device
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.