Was asked this question multiple times at interview.
Main two
Investment bankers/M&A financial consultants - they assess the financial projections for why the M&A deal should take place (e.g valuations like DCF's)
Accountants - involved in the financial due diligence of the transaction. For instance, are all the numbers the target are advertising like revenues/profits/expenses correct (see the notorious accounting fraud in the HP acquisition of Autonomy for more info!).
Extra
Tax advisers - I was told that tax advisors are also involved in a deal by an associate in the corporate team who asked me this question. Guessing if its a multi-jurisdictional deal tax issues can get complicated and may also need non-legal people involved here. Probably will get you some extra points if you mention this!
Perhaps there are more but those three will have you covered if asked!
