Personally, where traps are concerned I think that most of the Grimtooth variety are much too harsh and random. This may be a bit less realistic but I prefer to have my traps setup so that PC's can figure them out or have a fighting chance. I think the only Grimtooth trap I ever used was the pit of boiling wax with the stone golem guarding the bridge across the pit. Wax fumes are highly flammable and this particular stone golem is made out of flint. I used this in one AD&D 2nd Ed campaign with a party whose fighter had a +3 sword and whose Paladin had just finished a quest for a holy sword. Both of them were at that cocky "Nothing can stand in our way" stage, so I thought it would be interesting to see how they fared without being able to use their swords (see: "flint and steel")
Perhaps the most exotic one I have used often is a contingency-reverse gravity spell. A specific tile has the contingency spell on it... anytime a person is on the tile reverse gravity is cast. This is particularly fun in closed in spaces where the party is walking single file. *Pointing at character in lead* "You suddenly go hurling upwards and slam into the 20' ceiling" *rattle of dice for falling damage* "You have just long enough to catch your breath before you plummet to the ground" *rattle rattle* (At this point the other characters either have enough sense to grab their poor leader... or the above repeats... invariably with the leader frantically asking the rest of the party to grab him). The fun part, however, has just begun. The leader is usually a Warrior of some type and while hurt by this, can soak the (hopefully only) two successive falls. This of course is not necessarily true of the mage, for example, in the party. Some parties bust out with the rope and pitons at this point... on party actually had their warrior hurl the other members over the offending tile.
The one variation I have used to this was a room where the entire room reverse gravitied ten seconds after someone entered. This gave the entire party time to file in. To make matters worse, the ceiling was covered in sovereign glue and twenty seconds after the party entered the room the wyvern was released into the room. So generally whatever weapon was in hand was (hopefully)droped or (unluckily) stuck and the players then entered combat while hanging from the ceiling. I was nice enough to make this reverse gravity a one shot spell and the ceiling only 10' tall, though, as getting down was hard enough as it was.
Anyway I would love to hear your thoughts and stories on this =)