Dust and pollen for me.
Re: Zyrtec (from 11 years ago):
I used to use Zyrtec, until I discovered that if I didn't take it for one night I would have massive itching in my scalp, preventing me from sleeping. I looked it up and discovered that I'm not the only one that had these Zyrtec withdrawal symptoms. I promptly switched to Benadryl and have been happy since. (Benadryl is also much cheaper per pill than Zyrtec...when I discovered that three Zyrtec pills cost about the same as 24 Benadryl pills (~$8), the deal was even more sealed.
If my allergies are particularly bad and Benadryl still doesn't help I take a Sudafed as well.