I trained plenty of UU Pokémon just because I liked how they looked. Like Granbull, Exploud, Ursaring, Manectric, Kecleon, Meganium, Sandslash, Forecast, and Golduck. All of them have the correct nature, moveset and EVs. Their stats still were a little dissappointing of course, except for Ursaring's, my lvl 100 pokémon with the highest attack so far (390 Atk). Even higher than my Rayquaza (386 Atk), but thats just because Ursaring is Adamant, Rayquaza is Jolly, but still, 390 is pretty damn high.
I'm still thinking of training more UUs to lvl 100 like Aggron, Golem, Blastoise, and Grumpig. Specially Grumpig, I think he would be very fun as a tank (a mediocre one, but a fun one).
My build for it is:
Thick Fat
Bold Nature @Leftovers
EVs: 129 HP, 252 Def, 129 SDef
Moves:
Reflect
Psychic
Calm Mind
Confuse Ray
Reflect will reduce physical attacks by a lot and Calm Mind to boost my special defense and Psychic damage, which is pretty low since I didn't worry for SAtk EVs, but it'll get strong eventually. Confuse Ray can help me so that they hit themselves as I set everything up. Thick Fat already reduces Ice and Fire damage. Pretty slow strategy but fun nonetheless.
I haven't done this yet because I'll have to breed a bunch of piggies until one comes out as a male, Bold, and Thick Fat. I always want them to be male and with 3 things to worry about, chances get slower, and I'm too lazy to do it.