In the extra deck i play Constellar Pleaides, that can be summoned using two trap monster, the train package, useful to OTK, Cyber dragon Nova and Mechaba for the matchup against Dogmatika, Imduk, that can be useful to send a trap monster to the GY and many Punishment targets
However, some cards have ways of cheating monsters out of the extra deck without needing to use their proper materials, and Bahamut Shark is one of the most prevalent cards in this regard
Its strength can easily be identified in its useful removal effect and potentially high attack stat that is dependent on the number of monsters used for its summon
Tifa, Martial Artist* Another of the Final Fantasy 7 commanders, Tifa cares about the number 7, letting you get an extra combat if you hit with a powerful creature, a mark she can hit in games of 4 or more players without any special help beyond a couple other attackers
If there are obvious misses, don't worry - they might be in my "personal" top 10 list below