GDevelop is a perfect fit for quickly making games during game jams.
GDevelop is bundled with Piskel, a sprite editor that is perfect to quickly draw your sprites and for pixel-art.
GDevelop has an integrated sound effect generator, Jfxr. You can create sounds effects like explosions, jump, coins, power ups in a single click and customize them as you wish.
Want to create a retro platformer game? GDevelop has a pre-made behaviors that you can attach to your character and your platforms. In a few seconds you have a basic platformer game running and ready to be customized and enhanced! Other behaviors, conditions and actions can also be used to create any kind of 2D games: shmup, "Bullet Hell", arcade games...
Imagining and creating the rules of your game do not imply to learn the syntax of a complex programming language. The events editor displays a sheet of events: each events is composed of conditions and actions. When conditions are fulfilled, actions are run. It's that simple.