Mek with
KFF gives a +5 cover save to ground troops, nothing specail considering you can put them behind anything bigger than a lampost and get a +4 cover save
Meks with
KFF usually go with Mechanized lists, if your foot sloggin i would suggest a warboss. Lootaz are good light anti-vehicle but to take out the bigger stuff you will need Power Klaws, Warboss on a bike would be a fun way to do that (granted you give him some support)
Personaly i like this outfit for a Warboss
Warboss
PK, Squig, 'eavy armor, shoota/skorcha Kombi Weapon)
110 Points
A little pricy but throw him into some assualts and he can dish it out, some people dont like the one shot a game skorcha but it can soften up a squad really nice.
Edit:
I personally feel its mandatory for just about every squad of boyz to be led by a Nob with a
PK, for an extra 35 points you give your unit the chance to take out vehicles in assualts, that Nob can be pretty hurtful with that
PK.