Infernape is an excellent mixed sweeper. Lucario is more like a pseudo-mixed sweeper because of his unique sets.
Infernape@life orb
blaze
naive/hasty
232speed 24att 252spatt
-nasty plot
-close combat
-flame thrower
-grass knot
Infernape hits things hard with flamethrower and grass knot, but it can OHKO blissey, snorlax and other special wall with close combat. He can give teams a lot of trouble.
Lucario can be a little more creative...
Lucario@Life Orb
Steadfast
Naive/Hasty
252speed 252sp.att 6att
-Aura Sphere
-Dark Pulse/Shadow Ball
-Dragon Pulse
-Extreme Speed
Dark Pulse/Shadowball for psychic and ghost types that resist/immune to aura sphere. Dragon Pulse for Dragons. Extremespeed is a good finish move. He's not really a mixed sweeper but his sp.att moves are extremely unique and gives most common special walls like Blissey, Snorlax, Cresslia a lot of problems. And once their special walls go down the rest of their team goes down.