When Horatio is in the lab to make the comparison of the honey sample he collected at the club with the honey found on the body, a microscope is used and the samples are declared "identical." There is no way a visual comparison could reveal this - instead it would require chemical analysis.
When figuring out what the criminal's "fruity scent" is caused from, Grissom tells Katherine that it's because of Diabetic Ketoacetosis, which is treated with Novolin Insulin. This, however, cannot be the case since Ketoacetosis is, in fact, a very debilitating complication that can result from diabetes, which would either require extensive hospitalization or, in less severe cases, a treatment that would last, at most, a single day. Not only that, but Novolin Insulin isn't a specific type of insulin, it's a genetically similar to human insulin created by Squibb-Novo, making it a brand name instead of a treatment, and would, more than likely, be a constant running medication instead of just for the one condition.
When Doc. Robbins is explaining to Grissom how "Trunk Man"/Jason Doyle was killed, in the close-up of him pointing to the entry wound in the neck, you can see a vein in the neck pulsating.
Mina Rittle's corpse is clearly seen to be breathing when she is pulled out of the canal.
When Catherine is running through the house at the beginning of the episode, she runs past a mirror (or a door w/ a reflective surface). The camera and crew are clearly visible (evenif only for a split second via frame-step) in the reflection.