In cartoons, specifically cartoons of the Warner Brothers or Hanna-Barbera styles, bombs (Other than bundles of dynamite sticks) are usually depicted as a sphere with a short, narrow cylinder coming out of the surface at some point. The cylinder has a hole in it, which holds the fuse. When the fuse is lit, a small but bright spark races down the fuse towards the body of the bomb, and when it reaches the cylinder, the bomb explodes in the face of whatever cartoon character is unlucky enough to be holding it. Here's some ASCII art of a cartoon bomb, in case my description was insufficient:
_\/____
/\ \
!
!
|¯|
____| |____
/ \
/ \
/ \
| |
| Fill this in |
| with black. |
\ /
\ /
\___________/
| 
