I'd say the basics, in addition to a sound diet of course.
A quality protein powder (MRP or straight protein) when you can't get in real food.
Flax seed oil, or an EFA blend such as Udo's choice.
Antioxidants. I get my multi from the MRP's.
Creatine monohydrate is a nice option, especially since it's so cheap nowadays. The only side effect I have ever heard of from creatine is (water) weight gain. Since this is intracellular, it's a good thing since your muscles will appear to be larger and fuller. Doesn't work on everyone though.