Perhaps it would be appropriate to admit to some mildly OCD-esque behavior here, as I have knitted at least 55 pairs of slippers from this pattern with another two pair currently on the needles. The pattern can be found here.
If you know me, you most likely own a pair of these slippers. I've found that people are generally much happier about receiving a pair of these then one might think. I would consider them my most successful knitted gift.
I use size 7, 8 or 9 needles, often using a combination of up to three different yarns. I love mixing yarns - satisfies my artistic side - especially adding a shiny or glittery yarn like Vanna's Glamour from Lion Brand. Sometimes if I have a small amount of yarn left over, I'll just divide it into two balls and knit two slippers until it's all used up. So, it's an excellent pattern for using up scraps, also highly forgiving and easily adjustable.