ZMA = marketing hype
A homemade Zinc + magnesium + B6 combo will work as well
and, no, it does not raise Testosterone level
GABA : useless unless you take huge doses (a few grams)
forget it
Melatonin : works for some, no effect on others
Pretty good for jet lag
and there is no proven seconf effects if you take it on the long term (1 to 5 mg)