Offense:
mccree, if you can aim, you can 1v6, good damage close range/long range, stun, great 1v1er
Defense:
mei for sure, off-tank, wall, ulti, great for most scenarios.
Tank:
reinhardt - block, damage, charge, all around great champion for most scenarios,
Support:
Lucio - aoe healing, mobility, hard to kill, engages/disengages fights, disengages ultis (reaper, etc.)