This thread is similar to the Overrated Threats, except it's underrated this time. What are some Pokemon that people often ignore or laugh at, but it ended up sweeping their team? Do you have any examples of it?
For me, Arceus-Ice is fantastic in Ubers Rain. It's a versatile player. Once Rain is up, it has a Judgement-Thunder, BoltBeam combo. It can KO huge threats after it snags a few CM Boost, so much so that it can kill resisted Pokemon with its powerful Judgement. I think at +2, it can KO Dialga. I gotta refresh my memories. I wasn't sure what set the Dialga was running though.
Although Heatran is by no mean underrated, Magma Storm Heatran is probably one of the rarer sets seen. It can outspeed Politoed with Timid, and shut down the rain with the use of its own Sunny Day, followed by trapping it via Magma Storm, before finishing off with Solarbeam.
In NU, I've find Shellder a very hilariously strong Pokemon. It can beat a lot of Pokemon after it gets Shell Smash up. Wormadam as well. It has a really good typing and walls Garvedoir to the day the sun explodes.