Sometimes, I like to think up of different kinds of tentacles when I got the chance. Well, so far I only thought of a couple, but I think they are neat anyways.

Translucent tentacles, such as these here, shall be dubbed as the Sea Dragon.
They are a water based tentacle that have a surprising grip. Lubrication is no need with this tentacle; it's runny slime is thoroughly distributed. These tentacles commonly have a cool color, ranging from purples to teals. Very rarely would they be any other color. It can be used for both penetration and insertion. It may produce a more viscous, opaque slime, usually when penetrating.

I had another older idea for a tentacle breed called the Honey Suckle.
This one was rather bumpy and plump. They produce a thick, syrup-like slime that it's often confused with honey. It's only a little sweet and has a hint of aphrodisiac, only when a large amount will it take a strong effect. It tends to have a bulbous base filled with it's slime. Parts of the tentacles are translucent and opaque. They tend to have a yellow, warm color. This tentacle can easily trap and keep someone in place and feed it's syrup till their belly is stuffed.

Well those are my ideas so far. I hope to come up with more!