This simple activity practises vocabulary and to some extent speaking. Make a list of four or five words, all but one of which have something in common. Ask the students to find the "odd-one-out".
Don't be surprised if they come up with some surprising answers. Just ask them to justify their choice. You may well find it logical. Take, for example:
The answer could be dragon (because it is the only mythical creature) or cat (because all the other words start with "d").
Ideally, the students should phrase their justification in a form such as:
Here are some suggested words. You can easily find more. And one good exercise is to ask your students to create some lists (along with valid justifications).