Random holes can add a bit of instant history to any garment
Shift one stitch to a neighbouring needle, then continue knitting for a simple hole.
For a more dramatic effect, knit for a few rows, then drop the stitch in line with the hole
The ladder will not drop past the shifted stitch, and has no way to go above the stitch where knitting is resumed. One empty needle brought into work between two needles already in work will knit and be a secure base for stitches in subsequent rows.
If you don't want the ladder to bulge so much, just leave the needle out of work until you want to resume regular knitting.
If you would like a more pronounced hole, but without laddering, manual tucking using holding position on your machine is handy.
This hole has two stitches each moved to the next needle, then those two needles left in holding position until the needles were brought back into work one after the other in subsequent rows.
You can generate a lot of grunge effects with holes and ladders
Another way to subvert the regularity of your knitting is to make random tucks in the fabric by picking up loops from already knitted fabric and rehitching them onto active needles. For a skewed effect, shift the picked up stitches across the needle bed. A seven ended tool is handy for this, but your standard 3 ended tool, or even the 1 or 2 will be able to make interesting effects See the puckers in the picture above? That's the effect.
You can add a slash of contrast using short rows, then maybe confuse it with holes, ladders and puckers
You can also just manipulate needles by hand to work in differnt colours or textures
You could manufacture hideous carbunkles using this technique and an evil imagination.
Once you have knitted your piece, if it is not yet the statement you strive for, you can pick up a few stitches in the piece, ewrap across the picked up stitches and a couple of needles either side (if you want to allow for some curling in) and knit some tags
I played with this during a day of communal knitting. This is as far as I got when it was time to go home. Many techniques approached with a skewed point of view will adapt to a grunge aesthetic. Set free your inner punk.