Spoke breaks (coming soon)
Metal fatigue or big sticks can be to blame. Straighten up the wheel and ride on.
Ripped tire sidewall (coming soon) Sharp rocks can gash tires. Then the tube splurges out like a hernia. Not conducive to riding.
Flat tire, no spare tube (coming soon) This should be enough to teach you to bring spares. However, you can use what you have or natural resources to ride out.
Taco (coming soon)
The most descriptive term for a bike boo boo - the trail ate your wheel for lunch.