c43455065 魔力の泉
This card can be activated only if the opponent has at least 1 s/t card. (According to Konami database)

c9047460 BF－隠れ蓑のスチーム
The 1st effect can be activated onlt if previous position is POS_FACEUP.

c85771019 堕天使アスモディウス
The 2 tokens are generated at the same time, so the player must have at least 2 slots to sp_summon these tokens.

c69757518 CNo.5 亡朧龍カオス・キマイラ・ドラゴン
http://yugioh-wiki.net/index.php?%A1%D4%A3%C3%A3%CE%A3%EF.%A3%B5%20%CB%B4%DB%B0%CE%B6%20%A5%AB%A5%AA%A5%B9%A1%A6%A5%AD%A5%DE%A5%A4%A5%E9%A1%A6%A5%C9%A5%E9%A5%B4%A5%F3%A1%D5
The chain attack does not have count limit, and the target is restricted to monsters.