My Precious: WISH 23
What have pets and companions belonging to PCs and NPCs in campaigns you've GMed or played in added? What have their bad points been? How do they compare to sentient magic items in terms of their effect on play (good or bad)?
Okay, I'm going to snag first-answer on this one, which means I get to talk about Crabwaite first. (Well, in this context, anyway, I know MT and Rainbow K have both talked about him other places.) He's a lackey of one of the other characters in our current game, primarily run by the GM. It could probably get rather confusing if everybody had one, but as it stands, he adds quite a bit - mostly comic relief, but that's what he was there for. (You also have to admire a player who put, when it comes down to it, about 5% of his character into something he didn't expect any real gain from. On the other hand, Crabwaite has turned out to be, I think, more useful than anticipated.) At this point, it's hard to imagine the game without him. I mean, where would we keep our cheese?
One of my favorite pets was in an old, short-lived AD&D game I was in, where my character (a standard halfling fighter/thief, who kept insisting he was just a fighter despite the studded leather armor) had bought a well-trained guard dog. The GM had me roll a reaction for it, and it turned out we didn't get along. It would obey me - I'd paid for the training, afterall - but it didn't like me at all. The druid in the party, on the other hand, naturally got along with him quite well, which was reason enough to dislike the druid. That one roll, actually, was most of what shaped the character into a rather curmudgeonly sort who didn't very much like anybody.
Of course, cutesy disney-style pets on everyone's shoulders gets annoying, but generally speaking, I like pets. I'm speaking as a player, though. Meera assures me they cause far too much trouble for the GM. I can see her point, but I like them anyway.
Companions I'm not as big on - generally speaking, I do think an adventuring party should consist of PCs. The old hireling rules can be fun to break out if you have a big enough campaign for it, but...I prefer contacts, which let the GM feed the players hints without having someone else constantly tagging along, and still give the PCs a sense of knowing people other than...well, the other PCs.
In play, I suppose the main difference I've seen between pets/companions and intelligent magic items is that the former are more often the player's idea, while the latter are more often put in by the GM to be annoying. This is probably why GMs tend to prefer intelligent magic items. Goodness knows, Meera never complained about Glass, the neurotic holy sword she saddled my paladin with...but, hey, anything to keep the GM happy, right?