I've had many discussions with my doctor about vitamin supplements, as well as doing quite a bit of research on my own.
Two conclusions I've come to that my doctor agrees with - nearly everyone needs a vitamin D3 supplement. The last 20 years or so we've been told to avoid the sun (skin cancer), yet we need the sun to get a good amount of vitamin D3. The rate of deficiency of it has skyrocketed since folks started using sunscreen routinely. So, vitamin D3 (not the D2, which is not as easily utilized by our bodies).
Also, a vitamin B complex. To deal with the stresses that modern day life puts on our bodies. The B vitamins are essential for proper metabolism, hormone production, a healthy nervous system, energy production, as well as numerous other processes.
So, vitamin D3 and the B complex vitamins are the only one I take daily and the only ones that my doctor recommends I take.