The $90 WiFi Pineapple is now in its fourth iteration. The gadget does man-in-the-middle attacks on WiFi networks, allowing its owner to snoop on all the traffic, keylog password entries, and generally compromise the shit out of anyone using WiFi in the area. It's a damned good reason to use a VPN, like The Pirate Bay's IPREDator. Also: it has epic rickrolling potential.
The WiFi Pineapple Mark IV improves tremendously on previous models in both hardware capabilities and ease of use. Where the Mark III brought a completely redesigned web management interface the Mark IV continues with plug & play 3G / 4G connectivity, automatic presistent reverse SSH tunnels and a simplistic status page to name a few. The new control center shows at a glance connected clients hostnames, IP addresses, Karma'd SSID as well as signal strength, idle time and network throughput.
Hardware wise the Mark IV is built on a powerful Atheros AR9331 SoC at 400 MHz--over double that of the previous generation--and sports two Ethernet ports, 802.11 b/g and N connectivity, as well as most notably a USB 2.0 port, allowing for expansions like mass storage and 3G / 4G modems. *modem sold separately.
Also it's black, which adds at least 50 hacker points.