Stuff that annoys you...

when reading code not written by yourself. For example, I cannot stand it when  people use

if (condition)
    ...
else if (condition)
    ...
else if (condition)
    ...
else if (condition)
    ...
else

instead of the much more readable


if (condition)
    ...
else
    if (condition)
        ...
    else
        if (condition)
            ...
        else
            if (condition)
                ...
            else

>>5
else if is not a feature. it simply is an if statement nested in an else block. some languages however shorten it to a single statement, (e.g. python and elif) in which case it is a feature.