There are more conditions that are associated with chronic and low magnesium intake, the ones I listed above are the ones that affect me personally.

Here is a list that I found:

ADD/ADHD
Alzheimer's
Angina
Anxiety disorders
Arrhythmia
Arthritis- Rheumatoid and Osteoarthritis
Asthma
Autism
Auto immune disorders- all types
Cavities
Cerebral Palsy- in children from magnesium deficient mothers
Chronic Fatigue Syndrome
Congestive Heart Disease
Constipation
Crooked teeth- narrow jaw- in children from magnesium deficient mothers
Depression
Diabetes- Type I and II
Eating disorders- Bulimia, Anorexia
Fibromyalgia
Gut disorders- including peptic ulcer, Crohn's disease, colitis, food allergy
Heart Disease- Arteriosclerosis, high cholesterol, high triglycerides
Heart Disease- in infants born to magnesium deficient mothers
High Blood Pressure
Hypoglycemia
Impaired athletic performance
Infantile Seizure- in children from magnesium deficient mothers
Insomnia
Kidney Stones
Lou Gehrig's Disease
Migraines- including cluster type
Mitral Valve Prolapse
Multiple Sclerosis
Muscle cramps
Muscle weakness, fatigue
Myopia- in children from magnesium deficient mothers
Obesity- especially obesity associated with high carbohydrate diets
Osteoporosis- just adding magnesium reversed bone loss
Parkinson's Disease
PMS- including menstrual pain and irregularities
PPH- Primary Pulmonary Hypertension
Raynaud's
SIDS- Sudden Infant Death Syndrome
Stroke
Syndrome X- insulin resistance
Thyroid disorders- low, high and auto-immune; low magnesium reduces T4