On the list of gums that give me a headache, it's aspartame on the ingredients list. Believe me, I check. :)

Xylitol is actually pretty rare as the main sweetener in gum, it’s a lot more expensive. If gum mentions that it contains xylitol, check the ingredient list to see if there are other sweeteners listed first.

Xylitol is preferable because of its oral hygiene benefits, but most consumers are choosy enough to make sure their gum is exclusively xylitol.

There are some brands on Amazon that sell 100% xylitol gum if you go out of your way to find it though. Be careful with it around dogs though, xylitol is insanely toxic to them.

The ones I'm familiar with mostly use sorbitol. Though it's not uncommon to find aspartame on the 'less than 2% of the following' part of the ingredients list.

I just checked the gum in my backpack. Both Trident and Mentos gum have xylitol, sorbitol, acesulfame K, mannitol and sucralose. Mentos gum also has aspartame and maltitol syrup in addition to the others.