Findings:

• The last knock?
• I get knocked down, but I get up again
• The last man on Earth sat alone in a room. There was a knock on the door.
• All his front teeth knocked out, living a nightmare
• Postman's Knock
• Who Knocks?
• knock up
• The World's Worst Knock Knock Jokes
• Knock Yokoyama
• Knock Sensor
• engine knock
• The Vampire Always Knocks in Triplicate
• Indymedia sites knocked off the net by the FBI
• P Knock (user)
• Rot Knocks
• Who knocks within?
• Celebrity knock knock jokes
• A knock there was upon the door
• I call, but I never talk. I knock, but I never enter. I feel a bit insecure.
• Getting the wind knocked out of you
• opportunity only knocks once
• It's a Hard Knock Life for a Cosmic Horror Cultist
• I got the feeling the Fairy Council was mad at me when the president knocked over her coffee to get a better grip on my neck
• I knocked on the massive door, and came one step closer to knowing what I didn't know before.
• Knock knock who's there oh it's you
• The world will knock you on your ass. Are you ready for that?
• Knock it off
• Knock down ginger
• Knock On Wood
• School of Hard Knocks
• knock out
• Divinity School of Hard Knocks
• Knock down
• Knock off
• Knock over
• that old Philip Glass knock knock joke
• Front tooth knocked out!
• Knock yourself out
• Darth Everything meets Death who has just knocked on his front door
• knock
• Ask, Seek, Knock
• Knock on the Door
• If an Agent Knocks - Federal Investigators and Your Rights
• Don't knock it if you haven't tried it
• Three Knock Down Rule
• knocked up
• gene knockout
• Waiting for the knock
• Don't knock the glock
• Technical knock out
• The knock
• knock kneed
• push or knock
• Opportunity Knocks

If you Log in you could create a "oppotunity knocks" node. If you don't already have an account, you can register here.