Anatoly Karpov probably hasn't done any serious and sustained work on chess in over a decade, but give him a decent position out of the opening and he can still compete with just about anyone. There was a two-on-two rapid & blitz match this weekend in Cap d'Agde featuring Karpov and Valentina Gunina on the Russian side taking on the French team of Romain Edouard and Marie Sebag. The first two days were rapid chess and the third was blitz, and in each portion of the match a player would face the opponents from the other country with both colors.
The Russians won handily, 11.5-4.5, and Karpov was particularly successful scoring 7-1 overall, 3.5-.5 at both time controls. Of course he was a favorite against Sebag, but he went 3.5-.5 against both Sebag and Edouard, despite the latter's enjoying a higher rating in classical chess. Karpov basically played without openings (his recent advocacy of 1.e4 d5 2.exd5 Qxd5 3.Nc3 Qd6 is painful for me to watch having grown up seeing him at the cutting edge of opening theory*), but once that phase of the game passed he was one dangerous hombre.
There's a nice report on the event here (HT: Allen Becker), with games and videos.
* Yes, I know that was thanks to Semyon Furman and then Igor Zaitsev, but it's painful nonetheless.