Some of them took me SO LONG to figure out, there was one in particular that me and my girlfriend both knew, but couldn't for the life of us figure out until hours and hours of youtubing games we've both played. xD (She doesn't have a gamefaqs account and obviously won't be entering.)
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Come check out my work at Konami's Yu-Gi-Oh! Trading Card Game Strategy site!
http://www.konami.com/yugioh/articles/?author=14