There are plenty of pros and cons to vitamins. The obvious first answer is we should be getting everything from our diet and not have to take vitamins or supplements. While I certainly agree with this, it's not always possible.
There's also the idea that supplements help boost or prevent certain things at a higher dosage than we'd get from our food.
Supplements I take:
Krill Oil - Omega 3, and how they're put together make it easier to absorb than fish oil. I switched to this from fish oil because I was having trouble taking the fish oil pills (slight indigestion, fish burps) and these don't bother me at all. I would avoid these if you have sensitivities to shellfish as there's potential for it in krill oil.
Green Tea Extract - Piles of goodness in green tea. Antioxidant, anti-cancer, anti-aging, etc. You can get this in caffeine free pills as well.
Garlic Extract - cholesterol management, anti-oxidant, immune system, etc.
B-100 - Vitamin B multivitamin - healthy nervous system, energy, digestion, etc. Word of warning, taking this will turn your urine fluorescent (completely natural as our body is only able to store B12 for any amount of time, so the rest is washed out of the system). Not bad, just surprising at first.
Alpha Lipoic Acid - potent antioxidant and free radical scavenger that has been proven to regenerate Vitamin C and Vitamin E, restore levels of intracellular glutathione (an important antioxidant that declines with age) and increase excretion of toxic heavy metals such as mercury. Also has the benefit of helping your body by storing excess carbohydrates in muscle or liver instead of in fat cells.
Potassium - This helps maintain water balance, among other things, but this is the primary reason I take it.
Magnesium - Variety of benefits, but I also take it because it helps the body absorb the potassium