Cheese sticks. 

Thank you for all of the great ideas everyone!

GoingNuts, does he make his own jerky?  If so, I'd be interested in a how-to!

spacecanada, thank you for the recipes!  I will have to tweak them a bit, but I think I can make some of them work.

Pumpkin seeds (if safe) and sunflower seeds

We make energy bites with dates, sunflower or pumpkin seeds, hemp seeds, and sometimes coconut; blend it together, and form into balls.  You can add cocoa powder if you like to make them fudgey. 

You can also make granola bars using quinoa flakes or puffed rice and various seeds, chocolate chips, etc.

Also, this chickpea cookie dough dip for a sweeter protein snack:
http://chocolatecoveredkatie.com/2011/05/23/want-to-eat-an-entire-bowl-of-cookie-dough/
(We always make it with ground flaxseed.)

Edamame is high in protein and a tasty snack.

My kids eat dry cereal as a snack food. I think some are high in protein, and it is fortified with iron as well as other vitamins and minerals.

Jerky. 

(Personally?  Eccccch.  But DS has found it handy at times.)

If you're allergic to garlic, def make your own hummus.

Hummus.  Bean dips/spreads.

Sunbutter.

Does anyone have suggestions for high protein snacks that are nut free? (Also wheat & oat free.)