Smallest thing to make an LED flicker?

I'm just wondering what's the smallest thing I can use to make an 0603 smt LED flicker (not blink/flash)? I love the look of simply having a bad connection to the battery, but sadly that's not a very good or reliable method. I suppose I could use an AVR chip, but I've never done that before an it looks expensive to start. Any chance there's something like a flicker resister that I could just solder into my wire?