i've experimented with sending the guitars to a reverb bus with a nice sounding room IR, blended in just slightly. sort of mimics the effect of blending in a mic that's setup in the recording room, to give the guitars more space and a "live" feel.
be careful not to overdo it though. it doesn't work on every mix either. some mixes need the guitars as in your face as possible, with others you're creating an image of a band playing in a certain ambience environment (drum reverb, vocal reverb etc), and having the guitars completely dry sometimes just isn't right.
i'll do it on 2 out of 10 mixes, approximately.