So when we look at the planets we've discussed so far, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, do we find anything related to their magnetic fields that appears to be an anomaly?
Well, Mercury isn't an anomoly, more like "Insufficient data for proper analysis" - the MESSENGER probe intends to fix that. AFAIK the leading candidate is that the outermost shell of Mercury's core is still slightly liquid, due to tidal interferance by the Sun, which is significantly stronger on Mercury than the Moon's pull is on Earth.
Similar for Uranus' field:
Uranus - Wikipedia
Note that it may just be a property of massed hydrogen to generate a magnetic field, or something similar, and not just the 'big kids' like Jupiter and Saturn. Or it may be that some known, but as-of-yet undetected phenomenon is playing around beneath the planet's clouds.
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