Junkrat is awesome - he can be a total pain in the bum when he's played well. I joined a quick game as Junkrat on the weekend, after point A had already been lost, 24 eliminations, zero deaths and four gold medals later, the other team were cursing me something rotten
Same with Torbjorn - people might make a face when you select him, but set your turret up in a good spot, and you'll be getting cursed by the foe all day long. Annoyingly, it only ever lists your armour uptime when it comes to getting votes at the end of the day, even when you've smashed the other team to bits. Also, his rivet gun does plenty damage (up close he can practically one-shot many of the offence heroes with the secondary mode).
Both, of course, far more useful in defence.
To be fair, those two, plus Reinhardt and Mercy are probably the only heroes I consistently play to a reasonable standard. Pharah and Roadhog are on my work-in-progress list and I'd like to get Soldier76 reliable, but it's not coming together yet.