I've recently had a flurry of something calling itself Safari/7534.48.3. I was all set to dismiss this as a ludicrous fake-- even if they've jumped on the "new release every other week" bandwagon with a vengeance, there have to be limits-- and then I noticed that one of those Version Seven Thousands was myself on my iPad.
Huh. Fancy that.
Besides, the version number is on the left. Oops. Never mind, then.
On the other hand, the Genuinely Impossible Combinations include MSIE 5.5 for Mac, because they stopped at 5.23. And anything claiming to be MSIE on an Intel Mac is fake-- not because it won't run on Intel but because they stopped making it before the Intel existed, so the UA line will always say PowerPC. (I have personally tested this.)
And I recently got bitten by blocking MSIE [1-4] without closing anchor. Oops, sorry about that, MSIE 10 cutting-edgers.