What are some cards that switch your opponent's monsters into Def position?

Wow, there's actually a decent number out there, but here are a few of my fav...

Inferno Hammer (hence the avatar) - though he only gets to do it when he destroys a monster as a result of battle. Also puts it face down

Otohime - though a spirit monster, I used it a few times after Tsukuyomi went by the wayside. I surprised the heck out of a Horus deck by simply putting Horus LV6 on its backside and running over it with an Archfiend Soldier 8^D

Stumbling - There are tons of tactics with this continuous spell, though it will affect your monsters too

Book of Moon - A standard, but puts them face down.

I think my Pulverizing Anvils deck is around here somewhere, which went to abuse the tactic. Granted the decklist is probably pretty outdated (BoM in 3s wiht Tsukuyomi), the general idea is there.

Let us not forget Enemy Controller, perhaps one of the best. There is also Ready for Intercepting which only effects Spellcasters and Warriors.

Others include:

Swords of Concealing Light
Windstorm of Etaqua
Curse of Anubis
Zero Gravity

just to name a few.

Thanks, i want to make a deck based around Drilloid if i can get the cards..

You can't forget Stop Attack.