Here are some randomly selected joke topics
Penny
Knock Knock.
Who's there?
Penny!
Penny Who?
Penny For your thoughts!
Varnish
How do you get rid of varnish?
Remove the 'r'.
Tennis
Knock knock.
Who's there?
Tennis.
Tennis who?
Tennis five plus five.
Ghost
Did you hear about the ghost who last year went to Africa on safari?
He was a big-game haunter.
Bees
What goes hum-choo, hum choo?
A bee with a cold.
Walk
What is something that is unable to walk but can run?
A river.
Doctors
Doctor, Doctor I've just swallowed a pen.
Well sit down and write your name!
Bosses
Have you noticed that your boss is the only one who watches the clock during the coffee break.
Encyclopedia
I don't need to buy an encyclopedia - my wife knows everything.