There are tons of patterns and designs out there for girls but not so much for boys. Hats are pretty much all I see on the internet.

I designed this shawl collar vest for my boy a couple months ago. It is really easy to make and can actually work for girls too. The vest is created by creating the back and front panels and sewing them together on the side and at the shoulders. And then crochet the ribbing along the neck. Alternately you could create the ribbing first and then sew it. It can be made in any size using any weight yarn.

Let's get started.

Materials:

Yarn: worsted weight yarn or any weight yarn of your choice in two colors, just use the appropriate hook. I used Mill end bag from Michael's in Maroon as my main color(MC) and Red heart soft in Blue as contrast color(CC).
Hook: 5 mm, 4mm
Tapestry needle: optional.

My numbers below are for size 5T years, but like I said above you can use the size chart here to make it in any size (Remember to click on Boys on top, it defaults to Girls.). Also, measure the width of the piece and verify it against the chart.

Abbreviations: 

ch: chain

sc: single crochet

ss: slip stitch

hdc: half double crochet

YO: yarn over

hhdc: herringbone half double crochet - YO insert hook into next stitch, YO pull through and pull through the first loop on the hook too. YO again and pull through 2 loops on the hook.

hhdc2t: herringbone half double crochet together - YO insert hook into next stitch, YO pull through and pull through the first loop on the hook too. YO insert into next stitch, pull up a loop and pull it thought the first loop on the hook. YO again and pull through 3 loops on the hook.

Bottom ribbing (make 2): Worked with the smaller hook - 4.00mm

With CC chain 11.
Row 1: sc in second chain from hook and all the way across (10)
Row 2: ch 1 turn single crochet in back loops only (10)
Row 3-51: Repeat row 2.

For all other sizes: Repeat Row 2 until the piece is as wide as desired without stretching.

Back panel:
Row1: Join the yarn at the end of the ribbing with a ss and sc 51 evenly across the ribbing (51)

Row2: chain 2, turn, hhdc in the same stitch and every stitch across. (51)

Row3-47: Repeat row 2 (51)
Or until desired height is reached.

Front panel:

Row1: Join the yarn at the end of the second ribbing with a ss and sc 51 evenly across the ribbing (51)

Row2: chain 2, and turn, hhdc in the same stitch and every stitch across. (51)

Row 3-21: Repeat row 2

Row 22-28: Change to CC repeat Row 2 with CC

Row 29-34: Change to MC and repeat Row2.

Add in a few extra rows between color changes for larger sizes and decrease for smaller sizes.

Shaping the neck:

Left side

Here we are going to work hhdc2t stitches on the inner side of the panel in each row to achieve a slanted edge like a V shape on the left side. Join yarn to the left side of the front panel. 

Row35: hhdc 21

Row36: ch2, turn,hhdc2t,  hhdc accross (20)

Row37: ch2, turn,, hhdc accross until 2 stitches remain, hhdc2t in the last 2 stitches(19)

Repeat rows 36 and 37 until height is same as back panel or a total of 47 rows is reached.

Right side: 

Here we are going to work hhdc2t stitches on the inner side of the panel in each row to achieve a slanted edge like a V shape on the right side. Join yarn to the right side of the front panel and work exactly like the left side.

you must have 9 stitches un-worked on row 35. 

Seaming and sleeve edging:

Seam the Back and Front panels together leaving a gap of 14 rows or as desired for the armholes. With CC join at the seam under the arm and work 2 rounds of hdc along the sleeve.

Collar:

With contrast color. Join the yarn with a slip stitch at left side of the unworked stitches on row 35. 

Row1: sc in the same stitch and remaining 8 stitches in the gap. Join with st to the first stitch of Right side.

Row2:ch1, turn and work sc in BLO on the 9 sc from the previous row. 

Repeat Row 2 evenly along the right edge of the neck and 1 row each on the back and again evenly across the left edge of the neck.

Stitch the last row with tapestry needle to the row 35 of the front panel on the under side of Row1. 

Collar Edging: With MC, sc evenly along the neck.

Hide all the tails and the vest is ready : )

Hope my instructions were easy enough to follow! Enjoy!