The case for Maugan Ra is a compelling one.
At so-and-so amount of points, the players gets a lot of utility from a single unit. Most players keep him in cover, and use his multiple firing modes to the greatest advantage.
His Crack Shot ability, paired with his weapon: Guardsmen in cover? *pewpewpew* No cover now! This is also particularly useful in games of Apocalypse if the opponent deploys an anti-psychic beacon or similar strategem.
Fast Shot: Used in cover, he's useful for attacking low-value armor targets like Land Speeders and Rhinos. His rending ability gives a chance to put the heat on Terminators and Daemon Princes.
Since he's equipped with an Executioner (from the Howling Banshees), he gets a strength bonus and a power weapon. Paired with his initiative, he can pounce out of cover and overwhelm something small(ish) if he needs to. Or run and assist another unit responding to a powerful deep-strike. But don't charge him and others into cover!
All in all, he makes for several different roles on the table, and is worth consideration.