2 - pseudo-ASCII, as others have noted. It can be done reasonably well, but simple things that ought to work on ASCII (like copy-and-paste into plain text files) never seem to work. It makes taking notes or talking about the game in text forums into a pain. Also, pseudo-ASCII passes up a lot of "freebies" that you get with a term window, like automatic text resizing or font picking.
2 - Tiles-only. Lots of people prefer tiles, but two things that virtually all tilesets have in common are that many monsters look a lot like other monsters with a minor addition or palette swap, and you can't see very much dungeon around yourself because they're bigger than ascii letters. I really don't care whether a goblin is wearing a blue cloak or not, and ASCII doesn't bother to show me; it just displays 'g' for goblin. If I see a tile, I still don't care about the cloak, but it turns out the blue-cloak-wearing variety of goblin is actually something else entirely and I was WRONG when I glanced at it and classified it as some kind of goblin. Also, the short visible distances to the edge of the screen make much of the map invisible. And the simple things that ought to work on ASCII (see above) still don't work.
3 - game requires me to switch interface modes, ever. A game should require the keyboard, or a game should require the mouse. If the game requires both, then I am likely to not play that game. The moment when I have to transition from keyboard to mouse, or mouse to keyboard, interrupts my flow state and forces me to think about the interface. After learning it, I want to never think about the interface. Personally, I strongly prefer keyboard-only interface. Mouse-only interfaces are just barely tolerable. But mouse-only functions with no keyboard equivalent, and keyboard-only functions with no mouse-equivalent, in the same game, is a problem worse than a mouse-only interface in my opinion.
1 - Game requires me to touch the mouse, ever. I strongly prefer keyboard interfaces over mouse interfaces. "Point at" is a simpler idea, and tends to result in simplified games. I don't want the game simplified.
2 - Documentation (especially in-game help) missing or out of sync with interface. If the help describes the key bindings from last version, or the explanation of some feature hasn't been true since a bug fix 2 versions ago, or etc, that's worse than not having that documentation at all.
Bear