Okay, so here's some non-standard use of RDFS/OWL that Axel Polleres came up with:
rdfs:subClassOf rdfs:subPropertyOf rdfs:Resource .
rdfs:subClassOf rdfs:subPropertyOf rdfs:subPropertyOf .
rdf:type rdfs:subPropertyOf rdfs:subClassOf .
rdfs:subClassOf rdf:type owl:SymmetricProperty .
Full reasoning on this according to some ruleset (say pD*: -- i.e., OWL-Horst -- rules rdf1, rdfs4a, rdfs4b, rdfs7x, rdfp3) gives everything. I'll let you work that one out. By everything, I mean every possible (albeit finite) combination of identifiers that constitute a valid RDF triple: the number of resulting triples equals the number of unique identifiers, cubed. Stick those four statements into a web-crawl, do some happy-go-lucky rule-based reasoning and you have problems. Of course this is only one such example. Watch this space.
...oh, and before I go, it doesn't even take four triples (pD*: rdf1, rdfs4a, rdfs4b, rdfp6, rdfp7, rdfp9, rdfp10, rdfp11).
rdf:type owl:sameAs owl:sameAs .