I say best/ worst/ biggest/ craziest because often the Playmates accessories could be all of those things at once.
The most bizarre were often the most desperate, like issuing Orion Slave Girl Vina with a fountain, or just sticking a dilithium crystal in the package when they obviously couldn't think of anything else to include. My hat does go off to the Playmates people's imagination in giving Q a miniature Enterprise and miniature Earth (pity they never got to recycle it for a Gegen the Voth figure), which were at least conceptually appropriate.
Then you have the snap-together neutraliser chair thingy that came with the Andorian figure, which was both boring visually and rather pointless (also, I'm pretty sure it was too small to actually sit a Kirk figure in), although since the figure itself was a two-in-one affair, I suppose additional gear didn't matter too much.
Anyone else have favourites or least-favourites they'd like to nominate?