I often need to do such things as enter a column of twitter handles. But if I start a cell by typing "@", excel assumes its a formula, and worse, refuses to accept a bad formula.
Through experimentation, I found that I can set the whole column with a format of "Text" and that convinces Excel to accept the poorly formated "formulas". So this is a workable solution.
But I don't accept this as an elegant or proper solution, as it still assumes the input is a formula, and it acts as so (trying to sum other cells clicked, and such) until I force it to finish editing the cell. In other words, I don't trust the results of this solution.