I've brought $Tree ponchos in the past; if they've changed I guess I need to hit WM for better ones.
Other $Tree/Target $Spot items:
Shampoo/Conditioner
Toothbrushes (pack of 4)/Small toothpaste
Soap
Hand soap
razors ($Tree has 4-blade razors that are pretty good, imo)
lotion
(All of the above are "disposable" IMO and whatever is leftover is left behind or trashed - once that stuff is opened it leaks, and I don't want it getting all over everything on the trip home)
laundry bags (to separate dirty from clean in suitcases)
comb/brush (my good ones don't leave the house. Ever.)
shoe bag/over the door organizer
activity books/crayons for the car trip and cheap toys to keep kids busy in lines
Target's $ Spot almost always has character socks for little kids, and those characters are often Disney, so I grab any boyish ones I see.
I also tend to pick up whatever strikes my fancy that is more of a seasonal or "sometimes" item they carry; for instance I found glow-in-the-dark shoelaces for the boys there a couple of weeks ago - those got tossed in the Disney box. I'm there at least once per month, so I just pick up items here or there rather than making one big stock-up trip then throw everything into a plastic box with handles (also a $Tree find) so that I know where to find my "goodies" when it's packing time.
I buy glow bracelets/necklaces in bulk -
amazon has 50 for about $6.