No needle - usually a removable, sometimes curved, plastic tip. Here are some examples.

12 cc (I have this one but put it only in smaller kits):
http://www.nols.edu/store/product.php?productid=16249&cat=266&page=1

35-60 cc (I have a similar one that goes in my larger group kit - can't remember where I got it, and it has a green curved tip that's a bit smaller than that on these; it develops really good pressure for cleaning out wounds):
http://www.wildmedcenter.com/store.html#syringe

I've used these a fair bit in the field - great for cleaning out scrapes, skinned wrists and knees, and debris-filled cuts. You can improvise with a ziploc bag or hydration bladder, but they don't get near the amount of pressure going that the irrigation syringes do.

PS - a few water purification tablets might not be a bad idea as well, if you're not carrying some elsewhere.