• A 21-year-old with a sense of humor will get a laugh from a gag gift.Aaron Cobbett/Digital Vision/Getty Images
  
  The look on the face of a person opening a bottle of geriatric vitamins on his 21st birthday is priceless. Turning 21 is a milestone that some view as the true entrance into adulthood. For a friend with a good sense of humor, consider a gag gift to commemorate the occasion of his 21st birthday.
  
  

Rival School

• A 21-year old in college may feel passionate about the teams at his school. This school likely has a major rival. As a gag gift, get him an item with the rival team's logo on it. Just don't spend too much money, as he'll likely never wear it. Look for items on sale at a local department or discount store.
  
  

Homemade Gag Gift

• There's no reason to spend any money on a gag gift. Making a homemade gag gift is usually a simple task, so use your creativity to come up with something. If the birthday girl has an unnatural obsession with smelling good, poke fun at this by making a bag of hillbilly potpourri that includes items like spent shotgun shells, beer caps and peanut shells. To a friend or roommate who is always lying around, give a block of wood with instructions to put in the middle of the floor, walk around it and rest because he's just walked around the block.
  
  

Over the Hill

• While 21 is considered quite young by most standards, it may feel to the birthday girl like she's losing her youth. If she can't stop complaining about this, give her a gag gift of an item normally meant for older people. Get her an "over the hill" shirt or hat, a walking cane or a tube of denture cream.
  
  

Excuse Ball

• If your 21-year old friend always seems to have an excuse for everything, get him an excuse ball. These resemble the magic eight-balls that you shake. Instead of a fortune, a different excuse comes up in the window. These are sold by novelty shops and online retailers.