Magnaguards are the only melee troops on this list that aren't living, but that doesn't mean they are any less of a fighting force because of it. These battle droids were very skilled warriors that could rival Jedi with their powerful electro staffs.
They were very popular with high ranking CIS (Separatist) personnel such as General Grievous and Count Dooku. IG-100s typically fought in pairs and would be often sent on missions by their masters to kill Jedi. Count Dooku and General Grievous also used them to wear down opponents before engaging the opponent themselves.
They were also deployed as infantry on the battlefield, killing troopers with ease and taking many hits before being taken out. Magnaguards had very advanced armor and blaster fire would have a hard time destroying it. Magnaguards could also survive and fight without their head or missing a limb.
Their Electro Staffs were also top-notch and very lightsaber resistant. Magnaguards could also be seen sometimes pulling out a hidden blaster when the situation needed it. One of their other strengths was piloting. We see in the Clone Wars T.V show that they are actually really good pilots.
Overall I think that these droids were top notch considering the likes of Dooku and Grievous used them. I also love their versatility, being able to do a lot more than the average melee troop was capable of.