What's your favorite interface in adventure games? Doesn't necessarily have to be the most perfect or easy to use; just the one that you're the most partial to.

Off the top of my head, a couple of low-hanging fruit suggestions (feel free to add more):

• LucasArts "9 verb" interface (Monkey Island 2, Day of the Tentacle, etc.)
• LucasArts "verb coin" (Monkey Island 3, Full Throttle)
• Sierra "icon bar" (King's Quest V, Space Quest IV, etc.)
• Revolution "Left does/right looks" mouse buttons (Beneath a Steel Sky, Broken Sword, as well most Wadjet Eye titles)

Mine is actually the one in Leisure Suit Larry 7. You click on something and up comes a contextual menu of appropriate verbs. If it's a door, you can "open" it; if it's a button, you can "press" it; etc. — and it also has an optional text parser for inputting your own verb.