I've had good luck with stuff from Pomona Electronics. Not sure where they're manufactured, but they seem to spec them properly so they're made correctly and work.
-Pat
+1 for Pomona test leads and jumper clips. For just connectors though you want to stay with the big boys. AMP, Neutrik, Amphenol, etc.
same here, started to obtain few measurement clips from Pomona. Quality seems to be fine there, need to also use it longer time to see how it is in a used condition. In addition to Pomona I have some clips from Hirschmann.
I have had problems with "non-branded" cheap RF-adapters (even in the case those were bought locally). Those were UHF-BNC adapters series. Within series they did not match each other, mechanical tolerances were too big. I try to avoid non-branded RF-connectors...
My last BNC T-adapters I have ordered as Amphenol brand. Those have not yet arrived, I expect them to be good quality.
For RF connectors, I nowadays buy from well known brands. Couple of those were mentioned earlier - occasionally I use Suhner, Radiall & Rosenberger connectors & adapters.
EDIT (2017.02.16): BNC T-adapters arrived (Amphenol). Quality is good and fit to scope is OK. Those BNC male connector, have six sections of outer conductor...