OK, the number of shopping days 'til Christmas is dwindling, some of the merchandise at the malls has a picked-over look about it, and you still have nothing for that hard-to-buy-for person on your gift list. What to do? If the results of a survey in the latest issue of Choice magazine mean anything, here's what you should not do: make a present of an electric ice shaver. Choice, a publication of the Australian Consumers Association, asked 12,000 people their opinions on the most useless gifts to put under the tree for Dec. 25. By a 48 percent to 47 percent margin, the shaver - um - trimmed home ice cream makers for first place. "We always ended up with a big mess - and not enough crushed ice to be worth the effort," groused one unimpressed recipient. As for the latter, the finished product required "a lot of ingredients to make a very small amount " that was too soft, besides. What's more, both appliances take up too much storage space. Well, then, how about a foot spa? Ugh, no; that placed a close third. "Too much work for a few minutes of comfort," Choice editors wrote. Yet another dud: the aromatherapy diffuser. So what earned the highest marks for usefulness? It was a tie between ... toasters and tea kettles.