Stealth levels are the bane of the gaming world in my eyes. Boring, unnecessary and a pain in the arse to beat sometimes. Example in point is FF VII: Dirge of Cerberus with the Cait Sith level. Enjoyed the game up to that point, saw it was a stealth level turned it off and havent turned it back on. The stealthy gimmicky levels in games look piss poor compared to the purism of MGS or Splinter Cell.

Same goes for poorly implemented vehicle missions(aka Gears of war 1 and 2).