Fives:
Once you possess something (ie: a seat you are sitting in) you may call fives in order to maintain possession of said object
Shotgun:
When there is an unpossessed object (ie: a lollipop) you may call shotgun in order to attain possession of said object
The difference:
you cannot call fives for something you do not yet possess, and you cannot call shotgun on something you do possess.
Comparison chart
 | Fives | Shotgun |
|---|---|---|
| deadlyness | not tough | |
| Introduction (from Wikipedia) | A shotgun is medium sized firearm, designed to shoot multiple projectiles through a smoothbore barrel (a non-rifled barrel). | |
| Ammunition /projectiles | A shotgun shell may either contain several pellets or a single slug. |
Comments: Fives vs Shotgun