FELOTHAR, THE STEADFAST I saved potentially the most controversial card for last: Felothar, the Steadfast
Mental Misstep Banned in both Modern and Legacy, Mental Misstep is a free hard counterspell (because why bother paying mana when you could use life) for any spell with a Mana value equal to 1
The X/Y/Z bit is a bit bizarre, the artwork isn't quite as zany as it could've been, and the flavour text, presumably, is the actual WOTC customer service number
Plus, doing the sixth color in a set like Planar Chaos had the advantage of giving us the perfect excuse to stop immediately afterwards
#11 My parents got me this game when it first came out, but I didn't know how to play the TCG so I rarely used it
Heat Stroke MTG For three mana, Heat Stroke puts a really awkward restriction on the board, as it strongly discourages players from attacking and blocking