As Slimes are my favorite mob in the game I thought I'd brainstorm with you guys about a mod to improve on them. As of now their only use is making Sticky Pistons and Leads. Here's some of my general thoughts:
1) All large Slimes can absorb the first mob it touches to gain the characteristics of that mob.
A) Cow Infused Slimes will drop Sticky Leather which can be smelted to get regular Leather. They'll also drop Edible Slime which gives full hunger but afflicts you with Nausea IV for a minute.
B) Pig Infused Slimes will follow the first carrot it detects regardless of whether it's planted, dropped on the ground, or in a chest. They'll drop Edible Slime Chunks that give three hunger and Nausea II for fifteen seconds.
C) Chicken Infused Slimes will not take any fall damage no matter how far the fall. They'll have a small chance to lay Slime Eggs with which you can spawn a friendly small Slime. If you feed your new minion an Enchanted Golden Apple it will become a large Slime and will be able to absorb three mobs for their traits.
D) Squid Infused Slimes have infinite Waterbreathing and can jump on solid ground submerged in water.
E) Wolf Infused Slimes will deal double damage and take half damage.
F) Zombie Infused Slimes will not burn in daylight and will attack in groups.
G) Skeleton Infused Slimes will not burn in daylight and will fire Slimeballs at you that do twice the damage of an unenchanted bow. They will drop Slimy Bones which yield five Bonemeal each.
H) Creeper Infused Slimes will explode as regular Creepers do but will split upon exploding. The medium versions will repeat the process and the small versions will suicide on you, in total yielding an average of 21 explosions.
I) Enderman Infused Slimes will teleport like regular Enderman but are immune to water. They'll drop Sticky Pearls that can work like Ender Pearls, can be used as Slimeballs in crafting, or can be smelted to get Magma Cream.
Please feel free to post your ideas on what else could be added.