I happen to believe that they are one of the quintessential fantasy creatures, especially in rpgs.
Partly this is due to their significance as wild creatures of evil in Tolkien's works, but it's also due to the fact that one you get your head around what a giant spider would actually do to you, there really no need to introduce mind flayers, dragons or ettins into an rpg, as giant spiders are horrific enough.
Add in the fact that we can imagine them perfectly, I would always find space for a giant spider or three when I was GMing.
These little chaps are from Copplestone Castings and I've wanted to get them for years, but needed a reason. Rangers of Shadow Deep has given me that reason, as the next scenario features them heavily.
I actually have some similar sized spiders from Descent, but I quite fancied basing some to fit with my 7TV Pulp collection.
The multi-based spiders are so that I can add large spiders, count them as spider swarms or even just add a bit of variation to the tabletop.
I've also based up two new trees I bought to add a bit more variation to my woodland.
This little spending splurge included two mules, one of which is destined to become Bill the Pony for my Fellowship of the Ring, the other will be for general use, probably also in 7TV Pulp. I've also bought a couple more Batman miniatures. However, getting all of these done today keeps my tally healthy.