If you guess right in Frog (Finder|Legs), a frog is revealed. However, if you guess wrong, the square remains the same, and you can even guess it again. But the fact that the square doesn't contain a frog is important information (specially in Frog Legs) - having this information burried in the move list is awkward. If the game progresses at one move a week, it's hard to remember which games you have to scan the move list. Also, but this is a minor issue, the fact that a wrongly guessed square can be guessed again, this allows for a never ending game. (It may be possible that there are Frog Legs situations where it's "better" to guess a square of which you know there isn't a frog, than to make a move that reveals information).

So, I propose the following: if a square has been guessed, but doesn't contain a frog, the square is marked (perhaps with a cross, or a question mark), and cannot be guessed again. It still may be shot at (and then revealing the number of frogs surrounding it). This doesn't change the rules of the game (other than preventing guessing the same square twice - but that usually will not be what the player wants anyway), but makes it better playable.