If there are any, which cards let you look through your opponents deck. I want to know for my leech deck (in my sig.) how do i know that im taking their best monster when i havnt checked their deck to make sure?? lol.

There's Emissary of the Afterlife (provided they have no LV3- Normal Monsters), Dark Designator (can you say, "Weather Report"?), and Abyssal Designator (provided they don't have a match). There's probably a few others, but I can't think of them at the moment.

There is Deck Devastation Virus and Spell Vanishing that handles that department well.

What you need is Nobleman of Crossout and my personal favourite Arsenal robber. As most people seem to forget that Snatch steal and Premature Burial are equips, which means you can disqualify them in a tourney. :p

ya there are a bunch of cards that does that. however, this rule was never really enforced. we all know its there but people start saying "you can't do that!" yada yada yada. it's fun to see there faces when you say it though.

No, you couldn't simply disqualify someone for that. Half the reason why the opponent gets to look through if the player claims he/she has none of the said card is to make sure that the opponent isn't making a mistake. If a player states that he/she doesn't have the stated card(s) in his/her Deck, and the opponent finds out otherwise with the effect, then usually all that a judge will do is make a warning, NOT a DQ.

Disqualifications are ONLY for major infractions/repeated minor infractions. Never for one minor mistake due to player error.

There's also Chain Destruction. It's not exactly a card you would find in any ordinary top tier tournament deck, but if you are looking for a way to search your opponent's deck, it definately accomplishes this task. Here's one particular use for it: summon Breaker the Magical Warrior, then activate Chain Destruction on your Breaker. Most decks run a Breaker, so there's a good chance you'll deprive your opponent of his. Breaker is of little use once it hits the Graveyard.