LONDON—A big gainer these days in the Amazon U.K. sales ranking under “sports and leisure” is baseball bats. One customer review for the Rucanor aluminum baseball bat (its sales up 6,541 percent on Tuesday afternoon over the preceding 24 hours) suggested why: “Thanks to the ergonomic handle, one easy swing should be enough to shatter patellas, skulls, or any other bone on your targeted looter. Personally, I would recommend also investing in some fingerless gloves for extra grip.”