Hmm, depends on your budget and where you plan to go afterwards.
Top 5 for me at the moment (in no particular order).
1. Racine - french bistro, small + busy, great food (opp. V&A)
2. Nobu - still fantastic, but of course pricey and murder to get a table (Park Lane)
3. The Orrery - best Conran restaurant and Marleybone Village is good fun (Marleybone High St)
4. Axis or Indigo at One Aldwych - great location, fantastic lobby bar and really central (Aldwych)
5. Tuttons - cheap and cheerful, but food is reliable (Covent Garden)