I've seen some pretty original UU/BL teams, they are fun to battle. And actually, I too tend to whip out a few BL Pokemon of my own out of favoritism. Lapras, Steelix, Rotom, Scyther, and Flygon are all Pokemon I enjoy bringing into battle, and half my current team comes from that group.
Being unexpected doesn't always have to involve BL/UU Tiers, either. My most enjoyable Pokemon butt-whooping is watching Dragonite lay waste to a usual counter, especially Ice Beam equipped Ubers. There is nothing like watching Kyogre fall to an Outrage to win the match.
Why exactly do you find using one overpowered pokemon better than using a full team of them, or none? I'm just wondering.
Because it's the only way to allow a wide group of useable Pokemon without having to outright ban anything. There aren't a whole lot of 'mans that perform well in an Uber-centric battle. Hell, some of the Uber class doesn't even perform well in all-Uber battles. Giratina is virtually worthless because you almost never see another Uber who doesn't carry one of his weaknesses. And Garchomp, despite pjwning the OU tier, doesn't have the power to stand up to the likes of Groudon and Latios. The same to a lesser extent applies to Mew, who is deemed Uber due to being unpredictable, not for power. An all-Uber match is severely limiting and lacking variety, which makes for a boring way to play.
Using a lone Uber is a common practice with casual battlers, too. Most people who have an affinity for an obvious Uber will usually try to blend them into otherwise standard teams rather than throw all-Uber sets that invite complaints of cheap play. I'm currently engaged in such a PBR tournament held by one of Serebii's users. Why nobody in the "competitive" circles will acknowledge it as a valid format is beyond me.
Not to mention the all-Uber concept completely wrecks Double Battles. There's only so much you can do against a Scarfed Darkrai/Kyogre opener, and most of it involves Explosion.
My favorite tier is UU though.
I find it fun to see pokes you would never use ^__^
Man, do I miss Yellow's Petite Cup... Sunny Park Colosseum was a nice throwback, even if it makes Sneasel completely broken.
Also on DeviantArt, Rumble, DLive.tv, and the Fediverse (@freespeechextremist.com and @bae.st)