Hmm, it appears that the other event was closed a bit early (and thus this one starting early). It is only the 26th in PDT and not even close to 3PM of the 27th. Was this intentional? I had planned to submit my entry on the morning of the 27th, but I guess it is fine if I can't.
Regardless, I'll edit this post with my entry for this contest when I finish it.
Fan: Because it gets hot and fans are needed.
Water bottle: Water is also important.
Headphones: For jamming out in the heat.
Cactus: What else exemplifies the hot summer than a cactus?
Water gun: Your enemies will feel refreshed with this pistol...
(Xbox 360) Controller: As gaming is broad, consoles are needed as well as computers and handhelds.
Towel: Nearly everyone goes to the pool/beach during summer. This item is essential for both of those.
Hat: Shade is often neglected, but it is needed during these hot times.
Cleaver: In case of Zombies.
Chair: For both spinning around and gaming. A useful little thing.
Laptop: It's hard to play browser games without a computer.