This game is useful as a quick knowledge check
There are many free crossword generators available online, for example here. These can be used to create small crosswords for your students. You can create the questions as short definitions and the answers will be added in the crossword template. Often you can include a solution word or phrase from a number of chosen letters on the board. Another way of using this is as a vocabulary check, where the question part becomes the word in the source language (e.g. 'bucket') and the answer needs to be the word in the target language (e.g. 'Eimer'); or the other way around.
Necessary ressources: computer, internet, printer, paper