i totally feel this. i don't know much music theory, just go by ear.. some things i try which sometimes are good and sometimes horrid: (assuming sequenced/midi stuff)
automatic scale changers - eg the 'scale' midi fx in ableton live. record my cheesy obvious tune and map it to a different scale afterwards. sometimes only a couple notes get changed, sometimes the whole thing. (sometimes i map it to a scale with only 2 or 3 different notes in so the melody becomes a rhythm line instead).. occasionally come up with some really pleasing total mood changes this way, which i probably wouldn't have done on purpose.
arpeggiators - again, i often stick these on a tune i've already laid down & then tweak for unpredicted results, as opposed to setting up intentionally beforehand. can use them to change the timing, add little ornaments in between notes, set non-major-or-minor-key-preserving intervals so things sound wrong (maybe i put a scale changer on it afterwards to make it sound differently right again), etc. play the same tune through two different arps with different timing to catch/emphasise different notes & make more intricate rhythms. arp can sound too uniform & obvious as well so it's fun to automate it..
if i'm recording with midi keyboard (which, i can't really play keys, i just mess around with it) i try to just dwell on the feeling of playing it, the rhythm i'm playing instead of the exact notes. and wobble the pitch bend around in pattern-ish ways, like the pitch bend is a rhythmic element.
if it's a repeating melodic line - delete some of its notes. delete a couple. delete some important ones. delete all of them except three, whatever. then delete different ones next time. so instead of a tune which repeats over and over, it's like different parts of the tune are revealed at different times and ur brain can fill in the gaps..
.. so yeah those are things i try to do, which aren't as cool as being able to just come up with and perform interesting stuff intentionally.. but at least maybe can be a way in, or a way to get ideas.. =)