Any of the imported German Oktoberfest beers are malty but not very sweet. Negra Modelo, the Vienna lager from Mexico, is similar but perhaps a touch more sweet. Even the good old Sam Adams Boston Lager is reasonably malty but not very sweet. Munich malts and judicious use of caramel malts can contribute to malty flavors without being highly sweet. Mash schedules and attenuative yeasts also help reduce the sweetness that might otherwise be present. Heck..... any well made saison is actually quite malty without being sweet at all. Sour beers too can taste very malty but in this case, well, sour and usually dry and not sweet.