I have always found it endearing that guys need to check to be sure their balls are in place before they go out in public. I mean, don’t you know? 
Me, purse. And not just “pocketbook”, but one of those Mom Purses they sell at Target, with the multiple zipper compartments, like small carryon luggage. The ones that are big enough to smuggle a box of Dots, a baggie of pretzels, and a can of pop into the movies (
)
What’s in it? Hmm…
Left-hand main compartment: Money purse (bigger than a change purse), cell phone, Palm Zire 21 which has Chess Tiger installed on it, for those long bathroom visits away from home. The Palm also has a calculator which I use occasionally at Kroger.
Right-hand main compartment: Wallet containing important papers like the shopping list for my wedding, my Social Security card, my high school IDs from 1970-73, stuff like that. Oh, and it has credit cards, Kroger/Cub Foods/CVS savings cards, insurance cards, library card, etc., in it, too. Compartment also contains checkbook, an assortment of Bic pens, all of which do work, and a substantial wad of important papers such as my list of Delorme Gazetteers that I am slowly amassing at Barnes & Noble, and the phone number of the guy who rear-ended me in 2003 at Hickory Point Mall.
Central main compartment: Intentionally left empty to facilitate dropping keys into and retrieving keys out of without also bringing junque with them, which would then fall out onto the ground and be lost forever. And yes, I do tend to be anal about things, why do you ask? 
Zipper compartment on outside of purse, which is subdivided into smaller flaps with various things parceled out among them: comb, chapstick, coach’s whistle for emergencies, collection of church bulletin art torn off front of bulletins during sermons, offering envelopes, a small lavalier watch for when I don’t want to haul the Palm out to find out what time it is.
Zipper compartment on next-to-body side of purse: Kleenex. Mostly unused.
And yes, it is fairly heavy. But I need it all. 
ETA: And the Palm lives in an orange plastic tampon case. It was the only way I could find to keep the Better Half from taking it out and helpfully installing things on it for me. “But I don’t want to synch it with someone’s Blackberry! I just wanna use it to play Chess Tiger, and to compare toilet paper at Kroger!”
And the first time he took it out to do so, he said, “Hey, where’d you get the nifty Palm case? Maybe I’ll get one for mine…” and I told him what it was really, and he dropped it like a hot potato. Literally. Heh.