One I have been impressed with is the GloTorch using a 3M DayGlo yellow phosphorescent formulation that glows nicely all night after a day in sunlight (even at this time of year). About £10 online or sometimes much less if you catch one being offered on an eBay Auction.
We have had one for ages and I wanted to get another in case the first ever packs up. This isn't your average glows faintly green for ten minutes "glow in the dark" this thing really does the business!
The torch only takes AA batteries but its claim to fame is by being possible to find in the pitch dark when camping or in a power cut.
There is a smaller keyring using the same Glo plastic on eBay - the description there is nonsensical as it is physically smaller in length than a single AAA battery and actually powered by a Lithium cell.
Not at all bad for £3 (provided you ignore the description). (no connection to the vendor(s) just impressed with the kit)
Also in the Dayglo colouring line I have found these 32GB Neon flash drives handy (you can never have enough storage).
(Amazon.com product link shortened)86669797&sr=1-37&keywords2GB+memory+flash
Anyone else found other obscure, cheap but useful stocking fillers? (YMMV)
Click to see the full signature.