**Core Concept**
Meckel's diverticulum is a congenital anomaly of the small intestine, resulting from the incomplete closure of the vitelline duct. It is a common cause of gastrointestinal bleeding in children and adults. The complications of Meckel's diverticulum can be life-threatening if not promptly managed.

**Why the Correct Answer is Right**
The uncommon complication of Meckel's diverticulum is **carcinoid syndrome**. This occurs when the diverticulum contains ectopic gastric mucosa, which secretes serotonin. The serotonin is absorbed into the systemic circulation, leading to symptoms such as flushing, diarrhea, wheezing, and heart palpitations. The carcinoid syndrome can be managed with octreotide, a somatostatin analogue, which reduces the secretion of serotonin.

**Why Each Wrong Option is Incorrect**
**Option A:** Intussusception is a common complication of Meckel's diverticulum, not uncommon. It occurs when the diverticulum invaginates into the lumen of the intestine, leading to bowel obstruction.
**Option B:** Bleeding is a common complication of Meckel's diverticulum, not uncommon. It occurs due to the presence of ectopic gastric mucosa, which secretes acid and leads to ulceration of the intestinal mucosa.
**Option C:** Obstruction is a common complication of Meckel's diverticulum, not uncommon. It occurs due to the presence of the diverticulum, which can cause bowel obstruction.

**Clinical Pearl / High-Yield Fact**
Meckel's diverticulum can be a source of significant morbidity and mortality if not promptly managed. A high index of suspicion is necessary to diagnose this condition, especially in children presenting with gastrointestinal bleeding.

**Correct Answer: C. Obstruction is a common complication of Meckel's diverticulum, not uncommon. It occurs due to the presence of the diverticulum, which can cause bowel obstruction.