Gel is a common crafting material dropped by most slimes and Slimed Zombies. Gel is vital due to it being an ingredient in Torches, and is used regularly from the beginning stages all the way through to endgame scenarios. It is also used as ammunition for the Flamethrower and the Elf Melter, and can therefore be stored in the player's inventory ammo slots.
Though the tooltip says 'tasty and flammable', gel cannot be eaten. The only edible item it is used in is a health potion.
Gel will appear different colors in the player's inventory depending on what color gel was first looted in a particular stack by that player, i.e. appearing as green rather than its original blue.
If two differently colored stacks of gel are combined, the new stack takes on the color of the stack put onto the other, no matter the stack size.
The gel color will return to blue if you drop and pick it back up or exit a world and rejoin.
While nearly worthless on its own, gel can be monetized much more effectively (about 5 per 1000) with a Solidifier and 1 piece of wood for each six gel, by making Slime Candelabras. See the Making Money guide for full details.
Trivia[]
Black Slimes do not drop their own color of Gel, unlike many other slimes.
The "tasty" part in its tooltip may be a reference to the fact that gelatin is often used in different foods.
Umbrella Slimes are the only source of Gel that is not guaranteed to drop it all the time, having only a 97.78% chance of dropping gel instead of a 100% chance. However, they are still high enough to successfully farm Gel.