OK, I'll start off...
First of all Reed failed to realise that Hoshi was a Cylon...oh wait that's Battlestar Galactica.
In "Cogenitor" Reed lets a hot alien female fondle his phase cannon without using protection (I mean anti-radiation shields of course...what else would I be talking about?)
In "The Aenar" Reed destroys the second Romulan drone instead of capturing it intact, thereby losing all hope of finding out what race was behind the mysterious attacks.
In "Daedelus" Reed insisted on searching a darkened room for a mysterious intruder accompanied by a fellow crewman WITH NO NAME thereby guarenteeing his death.
In "Silent Enemy" Reed turned down what he thought was an invitation by a hot Asian babe to come to her quarters and sample her "hot plate".
"In A Mirror Darkly" - he puts on a red shirt.
In "Terra Prime" Reed not only throws up, he foolishly gives his vomit in a bag to Dr Phlox! Guess what's going to be in the doctor's next New Age miracle cure...
In "Singularity" T'Pol complains to Reed that she cannot access the encrypted command packet containing her clearance code without the clearance code that is inside the encrypted command packet. So Reed sends her an encrypted command packet containing another clearance code but T'Pol finds she cannot open it without the clearance code within the first encrypted command packet which must be opened by the clearance code inside the second encrypted command packet...(well not exactly, but it would have been a good comic scene).