I made this guitar cake for a friend's son's 7th birthday.
I used a large roasting tin, 14.5" x 10.5" (27cm x37cm) and made a chocolate cake from scratch using a Betty Crocker recipe, making double. I lined the cake tin with foil and then filled it half full, using the rest of the mixture to make cup cakes.
Once cooked and cooled I drew out a template for an electric guitar and then cut it out using a little pumpkin cutting saw. I first cut out a long rectangle from the end to form the arm of the guitar. Then cut around the body of the guitar and finally trimmed some cake to make the handle of the guitar.
As the cake was about 1.5" thick I didn't need to layer it and so dyed a tub of Betty Crocker Buttercream style icing with red gel food colour to ice the body of the guitar. I used a small amount of the icing diluted with water to make a "crumb-coat" and iced around the cake. Allowed this to dry before icing the rest. I then dyed about half a tub of icing the grey colour. It turned out a bit darker than I had wanted. I then assembled and iced the arm and the fret/handle.
For the accessories, I first rolled out a piece of white fondant icing and cut it into shape and lay that over the cake. I then used skittles and a chocolate fudge bar for where the strings attach. I cut a strip of fizzy chew to make the pick-up and Rolos for the nobs. I used a lollipop for the "twanger" and strawberry shoelaces for the strings. They were a bit disappointing because they are quite twisted in the packet and I couldn't get them straight.
I used black tube icing to ice in the frets and white icing to make the little dots. Then more skittles where the strings attach and (you can't see in this picture) but 6 jelly dots to make the tuner screws on the back of the handle. I then had some jelly lips that I added for rock-n-roll effect!