I suppose it's a little cliche, but Garbador is one of my least favorites. I just don't like trash/waste that much and I'm not a fan of its design. I haven't really bothered to use one, so I can't reflect on its usefulness in battle, but poison types rarely appeal to me unless they have interesting secondary types or something else to add to them (a la Gengar or Nidoking in gen I).
I also really don't like Watchog. Patrat was fine, but Watchog looks more like a cartoon character than a Pokemon to me.
I also don't really care for Woobat. Zubat was bad enough. Did they really need to make another annoying bat Pokemon for caves? I suppose its typing is a little more interesting, but still, between that and Roggenrola's constant Sturdy annoyance (though I like its evolutions), cave-dwellers really weren't too fun to encounter.