Tyrosine is a multi functional amino acid. It acts as a neuro transmitter so it can be very beneficial for treating depression etc. because of its mood enhancing effect. Many BB's take it pre-workout at 4-6 grams because it helps you really dial in to the mind-body connection.
As for weight loss, tyrosine increases your thyroid output naturally. Often it is combined with gugul lippids to optimize this effect. You could add some caffeine with it, but a better alternative would be synephrine. It also compliments any ECA stack as well.
Tyrosine combined with paba and beta-carotene can really help you tan better as well.