Hi IMHO i think the best walk around/travel lens need to cover a good wide angle and a decent telephoto. The current standard zoom range is 18-200mm. However this remains debatable since ea h photographer has his own preference. For me though the best walk around/travel lens is not one but two - at least. Since I am using 1.6 FOVCF body i prefer to carry the 10-22mm and the 24-105mm L or the 24-40L and the 70-200mm f4 L if weight is allowable. I prefer 10-22 + 24-105 because it is a lighter set. Of I would also be carrying my gorillapod over ylmy tripod.