Rockin' the tree.

Yarn: less than 20g sock-weight yarn.
Needles: set of 4 US size 2/2.75mm DPNs
Gauge: 15st and 20 rows to 2"/5cm

You'll also need a little bit of polyfill stuffing.

Using figure-8, CO 9 st (5st on one needle and 4 on the other).
K all sts, splitting over 3 needles.
Knit one round even.

Increase round: [M1, K1] around.
Work 3 rounds even, then another increase round. (36st)
Work 6 rounds even, then another increase round. (72st)
Work 12 rounds even, then begin decreases.

Decrease round: [K2tog] around.
Work 6 rounds even, then another decrease round. (36st)
Work 3 rounds even, then stuff bauble.
Work another decrease round, then one round even.

Cut yarn and thread through live stitches, pulling to tighten.
Make a loop at top of bauble and secure with yarn end.