The following list gives ideas of what hero to pick when your preferred pick suddenly gets banned, or when you love one hero but want to play a similar-but-different one.
Tidehunter = Timbersaw. Both tough, melee initiator-types with lots of nuke.
Lion = Lina = Ogre Magi. All are big nukers with big single-target ultimates.
Abaddon = Legion Commander. Both can be played as support/healer/semi-carries, with slightly different functions, but very similar ability to buff and heal allies.
Wraith King = Sven = Dragon Knight = Alchemist. All three have hard disable, good tankiness and passive buff.
Magnus = Beastmaster. Tanky, big teamfight ultimate, buffing abilities and push.
Shadow Demon = Bane = Pugna. Okay, this is more of a stretch, but all of these are utility supports with an initiating ability, defensive ability, and good sub-abilities on low cooldowns.
Storm Spirit = Puck = Batrider. All three are "pounce in and isolate" type of ganker / initiators.
Earthshaker = Sand King. Stun to initiate and followup with big damage.