Onderzeeboot
Ecstatic Orb
This one depends a bit on the group that is drafting. If it's an experienced group, blue is often overdrafted and green underdrafted, which leads me to pick Sylvan Library, as it's one of the coolest reasons to be green around. If it's a casual group however, green is more likely to be overdrafted, and blue might be more open, in which case I would pick Vendilion Clique, an evasive 3-power beater with a super useful ability, not only because it gets a good card out of your opponent's hand, but also because it gives you information! Also, flash works really well together with counterspells