Here are some of my favourites!
Female fireflies attract males with a precise courtship signal. I don't know whether to be impressed or sickened, but the guys rather deviously waggle their bum to look like females, luring males in, then scoff them. "Look, its Dave! Mind you, I am hungry..." (proceeds to waggle bum like girl).
These guys have got the weirdest way of hunting ever; they literally fish for their prey like spiderman would the green goblin. I therefore dub it the spidermanspider.
(btw I don't have flash at work so I haven't actually watched this! Please someone tell me if its inappropriate!)
Rather deviously, they pump out specific female moth pheremones to catch the prey they want.
Portia fimbriata jumping spiders
These guys hunt other web building spiders that can be up to twice their own size. These guys have many tricks, such as disguising themselves as leaves, and hiding from their prey and sneaking up from behind.
Pretty clever, I think you'll agree, but what makes them truly devious is their acting ability. They sit at the edge of another spiders web and literally pretend to be prey, by tugging on the web in a very particular way. Portia makes web signals by stretching, plucking and striking the silk with specialized leg, palp and abdomen movements. These signals may either lure the resident spider to within attack range or keep it pacified while Portia sneaks up on it.
Portia even synchronizes its movements across the web with periods when the resident spider is distracted by its own prey, and even has the ability to detect web signals impaired by a light breeze hitting the web.
You might not think that much can beat that, but I would say that it is; meet the assassin bug.
The assassin bug does much the same as the Portia spider, but it is much more impressive considering that it is an insect rather than a chelicerate like Portia and so has really had to learn this from scratch.
It also has a few rather gruesome tricks up its sleeve. Assassin bugs have a penchant for injecting concentrated saliva into the body of their victim, liquifying its innards, which the bug proceeds to slurp up like a smoothie.
They also quite like dressing up. Assassin bugs have been known to cover themselves in sticky plant juices to attract and trap prey, and also to camouflage themselves by coating themselves in dust and leaf litter.
My favourite trick, though, is when their camouflage is the corpses of past prey. Ingenious, but decidedly gross!