I made this Easy Guitar Cake for my friend's 17th birthday. He plays guitar so it was perfect for him. I wanted to make a cake without fondant, since I'm not a pro at this. I'm really happy with how it came out, and it was really EASY--no special materials, no special molds, just a fun and simple project. If I could do it, you can too!
To make the shape of the guitar, use two 8 or 9 inch round cakes. Cut a small section out of one of them, so you can stack them together (like a Venn diagram). This is the base of the cake. To get the brown colored top, I used 16 oz of vanilla icing mixed with a spoonful of chocolate (for color) and a few drops of yellow food coloring. Cover the whole top--but NOT the sides--with this. After you've got it covered, go up and down vertically with the back of a spoon, so it looks a bit like the grain of the wood.
Then cover the sides in chocolate icing. To get the shape of the "hole" in the middle, I pressed the lid from the frosting can into the icing to make an impression. Then I put the chocolate icing in a Ziploc bag and cut off one small corner, so it would squeeze out in a line. I went around the circle impression with that, then carefully spooned more chocolate frosting into the middle of the circle and spread it out to meet the edges. I ended up using the extra chocolate icing in the bag to go around the edges of the cake, where the two colors of icing meet. That made it look a bit neater.
The neck of the guitar is made from upside down Kit Kat bars, stacked 3 high on top of each other. There's also one Kit Kat bar below the hole, for the base of the strings. The strings are made from vanilla icing, put in a bag with the corner cut off (like the chocolate before). Once you've put on the strings, you put yellow mini M&M's at the top and base of each string.
The tuners for the guitar were really easy. They were just pretzel sticks stuck into marshmallows, with the other end of the pretzel stick stuck in between the Kit Kat bars. Because of the Kit Kats' odd shape, you will have lots of small, convenient holes to stick the pretzels in.