Strong/Sudden:
* It felt like a small explosion went off right next to you.
* It was like a mini-earthquake shook the ground.
* It was like a cannonball was fired in your direction.
Uncomfortable/Startling:
* It felt like a shockwave ran through your body.
* It was like someone punched you in the chest.
* It was like a tiny bomb went off inside your head.
Funny/Lighthearted:
* It felt like a little bird flapped its wings in your face.
* It was like a tiny firework exploded in your ear.
* It was like a tickle monster jumped out of your nose and shouted hello.
The best simile depends on the intensity and nature of the sneeze and how it affected the person.