1. Grant Gustin
From the moment Barry Allen introduced himself and impressed most of the Arrow team with his deductive and forensic capabilities I was already feeling strongly towards Grant Gustin's casting. As the episode went on my confidence only grew further as Grant displayed a great talent for comedic timing, shy awkwardness and dramatic scenes. I particularly really enjoy the scene where he confesses to Oliver and Felicity the real reason behind his visit to Starling City and the story of his mother's murder. Gustin played the scene very well and it is easy to see why CW has already greenlit a Flash pilot based off this episode. Gustin's age was a factor which people did not take much liking to as he's fairly young, much younger then Stephen Amell and Oliver Queen. It was nice to see this called out as Oliver sarcastically asked if his parents knew where he was as well as the reveal he wasn't a fully fledged CSI, but rather an intern assistant to one. It made Barry's story much more believable and the character himself relatable. Another notable aspect is how his appearance tied in to the overall story. Whenever Smallville, for instance, had a DC character appear it was usually just as a cameo rather than a true appearance which built up to something bigger. The later seasons somewhat changed in this regard as other heroes appearances were part of the proto-Justice League, but it still came off as a cameo for the sake of a cameo. Barry's appearance in 'The Scientist' truly built upon events which had come before and laid more foundation for what is to come, giving the episode a credibility Smallville often lacked when introducing other heroes. This only leaves me excited for how his story will wrap up in the next episode and lead into his solo series next year.