Depends on the audience. Also, this is for small to medium firms (10-40). Can't say about the large 50+ places, I assume they would have separate account management and creative departments without much mix.
Cold calling, trade show (which is just a variation of the cold call) - we have a salesperson.
Initial pitch - salesperson + director/partner + maybe senior manager
Additional projects after the initial close - senior manager
New departments within old client - salesperson + the senior manager who handles existing account + maybe another senior manager (only if new capabilities are needs, old projects were ID, new project is UX)
Least, that's how I rolled.