I played a conjurer in 3.0 who exclusively summoned demons and devils to fight. He took a lot of flack from 'good' characters for working with demons, but he just pointed out that its better to force an evil creature to fight and die than enslaving a good creature to do your bidding.
Also, he had a bit of an ego and something to prove, so he bending a demon to your will and forcing it to do good showed his power.
