Dense Thug (comedy relief; WB cartoon character was named Mugsy), saying things like 'Duuuh, yeah boooss', 'Duuuhiiiiiieeedunno', or 'Shoo' t'ing, booooss'.
Mr. Monosyable. Most responses are words of one sylable (three at most), most responses are a single word (no more than three). Now, this doesn't sound like much of a voicepack, but it would be personality-driven. It could substitute for Batman, The Shadow, The Spider, The Punisher, or similar character. How much personality can an actor get in one word?
Southern Gentleman
Mr. Nervous (like Don Knotts' old character, much of which became Barney Phyffe)
Female Patriot might be good too.