Here are some randomly selected joke topics beginning with the letter 'N'
Nag
How many men does it take to screw in a light bulb?
Only one, but you have to nag him for a fortnight first.
Nature
Fred: My girlfriend loves nature.
Dave: That's very generous of her, considering what nature has done to her.
Nail polish
How many supermodels does it take to change a light bulb?
None - "Do you want me to ruin my nail polish?"
Nametags
Why do witches wear nametags?
So you can tell which witch is which.
Nature
Do you still love nature, despite what it did to you?