Oracle undocumented trace parameters

Do you know that there are more than thirty not documented and hidden parameters for tracing?
You can find them with this query:

select 	ksppinm "Parameter Name",
		ksppstvl "Value",
		ksppstdf "Default",
from	x$ksppi x, x$ksppcv y
where	x.indx = y.indx
and		ksppinm like '/_%trace%' escape '/' ;

Note that Oracle 9i has about 26 parameters (if I remember right). Oracle 10g has 35 parameters. Not yet test on 11g, I’ll do it. Also some parameters are only RAC related as _ges_trace (for GES/GCS trace)