I think Slimes need something new to make them more interesting.
What if they could reach high places, by doing a "Super Jump"?
- Small slimes don't super jump (so they can be kept as pets more easily)
- Medium slimes super jump 2-3 blocks
- Large slimes super jump 3-6 blocks
How it would work, is that they would basically stop for a second and charge up a higher jump.
Magma Cubes would probably also have this ability.