I've been thinking a lot about this crazy new range of Behringer pedals, wondering if it is possible to copyright the look, shape and colour of a product.
In the 1980s, Gibson tried and failed to sue a load of companies producing Les Paul copies, but last year, they (bafflingly) won a judgment against Paul Reed Smith for making a very vaguely Les Paul-ish guitar (lengthy judgement here).
Headstock designs seem to be copyrightable. In the 70s, Gibson succesfully sued Ibanez and Tokai (who briefly had a "Les Paul Reborn" model), and Fender have done it several times.
Roland Corp (who own Boss) are pretty litigious: They've sent cease & desist letters to people making VST's with the word 'Juno' in the title, and sued Synthplanet.com over copyright and grey imports.
Behringer have had legal run-ins with Mackie and Aphex in the past.
Boss themselves had trouble. In the 80s, they released the SF-1 Superdistortion Feedbacker pedal. DiMarzio sued, because they made "Superdistortion" pickups, so it became the DF-2 Super Feedbacker and Distortion, which really doesn't sound so good.