I just worked on a song that made me wonder what out of the ordinary processes you've tried and had success with. Sometimes it takes a little something extra - beyond straight EQ and compression - to help out those "special" mixes.
There are the the more typical ones like parallel compression or harmonic based devices such as the Crane Song HEDD unit that can work wonders.
In this particular case, I used a slight touch of reverb and blended it in to open up a mediocre recording and mix.
I thought it might constructive if we mentioned some of those times when we had to get creative.