It was an attempt at a humorous "motto" in the SCA. Taste Plate Mail. As in: I'm about to pummel you with my armor/shield.
Ah, gotcha. Well, if you want to make the grammar work, you need to put the verb in the imperative case, so you want 'guste' (singular, if you just want one person to taste the plate) or 'gustate' (if you want everyone to taste the plate) rather than gustatus.
Then, you need to change the plate mail from the nominative to the accusative case. While you're at it, you want to make sure you are saying 'plate mail' in the way you want to say it (with plate as an adjective and mail as a noun), since right now they are both nouns. I think you could just drop the 'lamina' and use the 'lorica', since 'lorica' itself can mean breastplate. Either way, you will need to change 'lorica' from the nominative to the accusative case.
So, the pithy version would be (and I kind of like this one best, since it is short and sweet, like the best of Latin usually is):
Guste loricam!
This would be you telling one person to taste the breastplate/cuirass. If you wanted to tell multiple people at once, it would be:
Gustate loricam!
And if you wanted to get really fancy and specify a plate metal breastplate, then you might say:
Guste loricam segmentatam!
(Lorica segmentata being of course the name for the classic Roman armor made of overlapping metal plates/bands).