A really quick starter to wake students up as soon as they walk through the door:
Draw a naughts and crosses style grid.
Write 9 different words or phrases about a topic.
One pupil comes to the front and can see the words. The rest of class has 1 minute to call out what they think the keywords are and the person at the front crosses them off as they are called out.
If there are any words left at the end of the minute the person at the front has to describe the word until the class says it (like articulate.)
It can also be used as a plenary and different students can be tasked with coming up with the 9 most important words of the lesson. This is a really low preparation activity but can be very effective at livening up a class. It is also a great AfL activity as it allows the teacher to identify what students view as key learning points in a topic.