David is...

...the devil
...burning
...triumphant over Goliath
...currently a hot property in the character actor business
...also currently hard at work
...kind to Mephibosheth
...presently on secondment to the Defense Advanced Research Projects Agency
...a big WWF and WCW fan
...considered by peers to be the world’s leading authority on raw food nutrition
...today found in all synagogues
...a superb literary achievement
...in the studio this summer
...simply the best
...sincerely sorry for the pain he has caused in the past

Marcus is...

...a frequent lecturer and conference speaker on computer security topics
...tired
...walking
...blind
...resurrected
...responsible for cruelty, suffering and death
...an up-and-coming voice in the movement advocating vegetarian diets on health, humane and ecological grounds
...a weird 12-year-old boy with problems at home and at school
...single, and lives with 5500 books, 1000+ games and supplements, and four pets
...indeed a lucky guy
...rolling in his grave
...a bit of a dipstick
...much bigger than Curtis
...getting old and getting scared of all the youngsters in his neighbourhood

[David is sincerely sorry for pinching this link from Meg via Nico]