Ok, after seeing Builder's awesome riddle, which I solved (ok, not really), I figured I could be nice and make you think of two at once.
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You have 8 identical Blue Lobsters and one balance. Lets say it looks like this.
One of the lobster's weighs slightly more than the rest, but you can't tell by holding it or anything. You are overcome with the sudden urge to know which one is the one that weighs more. Warning though, you have only time enough to use the balance twice before Netham attacks you with a Banana Razor! How can you tell which is the heavier?
Same rules apply to mine as his. There is no trickery.
You can't just say 'Oh! this one feels like it might weigh more.
Good luck.