When I'm playing competitively, I usually try to use whatever will work the best for me. If one of the best choices is a favorite, then heck yeah, I'm using it! But if my favorites won't cut it, then I just won't use it. Since I don't really hate any particular Pokemon (bar maybe a couple), I usually don't have to deal with a Pokemon that I don't like to use. Of course, sometimes I'll use a favorite on a gimmick team just for the heck of it. Back in 4th Gen, I used a team based around Agility Blaziken. Was it a gimmick? Yes. Was it fun? Shoot, yeah. But when things get serious, I'll just go for the smart choice, whether it's my favorite or not.