Fulsome. It is not a spiffy way of saying “thorough” as some believe (i.e. “We will conduct a fulsome review of this issue”). It actually means “flattering/excessive/lavish” (likely not the intention of any review). Sometimes people substitute “wholesome” for “fulsome” which adds something healthy to the discussion.
Irregardless. Use “regardless” and save yourself two characters.
Very unique. “Unique” requires no modifiers; if it’s truly so, it is.
Compliment/complement. If you talk about your “staffing compliment” you’re not talking about the number of your staff.
Gambit/gamut. One means “strategy” and the other means “range.” You can say “the full gamut of our gambit” but the reverse borders on nonsensical.
Tortuous/torturous. If using them to describe a process, keep in mind that one means “full of twists and turns” and the other denotes something a bit more painful.