[ From: firstname.lastname@example.org (Graeme Griffiths) ]
[Note: a similar variant.]
Dunno if this is one of the above, we call it Half-Its. You chalk the names across the top of a table like so.
Bill Dave Ted Victoria 20 T 19 D 18 41 17 TC 16 O 15 B
Each turn everyone goes for either scores (20,19,18,17,16,15) scoring on singles, doubles and trebles), any treble(T), any double (D), score exactly 41 in three scoring darts - three separate beds (41), three different colour beds (TC), outers and bulls(O) or bulls (B) depending on which round it is. You score the value you get on the round you're on. For example, if you're on twenties and you score a single twenty, a treble twenty and a single one, you'd score 80pts - the one is ignored. Similarly if you manage to score 41 in three scoring darts, three separate beds you score, surprisingly, forty-one. If you fail to score in a round your score is halved.
My team plays this after league matches with the opposing team if they're willing, team members' SO's and any other assorted drunk we can find. Its quite a silly game as you only need to have one bad round to drop behind but with the novelty rounds you can get lucky and catch up.
You can also invent your own novelty rounds like scoring exactly 4 with 3 scoring darts or inner 17's.