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And here's the most obvious one:

S = Normal singularities

One can of course also include seminormal and weakly normal.

EDIT: You can also add S2 (and thus the operation of S2-ification). Note that all of these have \emph{finite} "resolutions".

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And here's the most obvious one:

S = Normal singularities

One can of course also include seminormal and weakly normal.