Ceramics
While dedicated sales of English and Continental ceramics are rarer beasts in the saleroom calendar these days, the traditional mixed-discipline regional sales are a repository for plenty of material from the main factories of the 18th and 19th centuries.
Although the performance of much of this material does what it says on the tin, keen-eyed bidders aided by the reach of the internet can winkle out less obvious prizes. And if enough people spot them (although only two determined contestants are actually required), their scarcity will be recognised in the final hammer price.