I like to draft with preference to removal cards and what I call the 'surprise cards', cards that are difficult to play around unless you are either paranoid or have inside information via mind vision or the like. Things like dark iron dwarf, lance carrier, shattered sun cleric, that can let a crappy minion kill a good one, can really turn the tide. There is probably no 4 cost common minion I will take over dark iron dwarf, and that includes yetis and piloted shredder. (If I had good mech synergy, I would take one of those instead, but that's about it)
Class specific ones like seal of champions (there's a lot of OP paladin ones in this category, which is why paladins do so well), demonfire, velen's chosen, auchenai soulpriest, fallen hero, are examples of cards that let you suddenly make better trades on board without giving your opponent a chance to respond. Of course, you can't take too many of these, or you just have a hand full of them, but in arena, you probably won't get offered enough for that to be an issue.