Over time Killed by Death has grown on me. Think its a really solid episode overall. I would keep that one out of the three. Bad Eggs is solid too, but less interesting to me. Think Killed by Death does more with the characters.
Some Assembly Required is gleefully macabre, which I always like. I have to admit, I do in fact feel sympathetic to the dead football player. The moment where he's hiding under the bleachers watching his old team play, without him, knowing he can never have that life back...it's cheesy, sure, but it gets to me. And I like the dank warehouse hideout at the end.
Killed By Death is a really good episode. I don't like that it creates a character who is REALLY IMPORTANT in Buffy's back story, yet never referenced outside the episode--that's contrived--but taken on its own merits her cousin's death is pretty scary. And I love Xander being such a dedicated friend to Buffy and making it clear to Cordelia that he just wants to help her, not bang her. In my person head canon Xander is over his romantic feelings for Buffy by the time season 2 starts, though I know the show waffles back and forth on that point.
Bad Eggs can go. It's not a bad episode, but it doesn't stand out at all, either.
Maybe my frustration is more about the larger TV trope of suddenly introducing a plot point that ought to be a pretty big deal, using it as convenient for plot purposes, and then immediately discarding it. I think it's kind of lazy, in a way that BtVS doesn't tend to be. If I'd seen my cousin die screaming in front of me when I was just a kid, I'd probably be haunted by it for the rest of my life. But I guess I'm not a slayer either. In the grand scheme of things, it's a minor complaint, not important enough to really affect my enjoyment of the episode.It was important in this episode and added something to Buffy and the plot. Besides that I wouldn't see much point in them referencing it outside of the episode.