I searched a bit for "silent r's" in Old Norse
and quickly found many sources (all of them SCA,
I think) telling tales of silent and "nearly silent"
(whatever that means) r's. As I stated before this
is incorrect. :-)

Kveðja,
Haukr

- - -
"The final 'r' in <Thorvaldr> is nearly silent."

"Gareth is often confused with Garth [1], but the names
are unrelated in origin. Garth has two origins. There
is a fairly common Norse name, Garðr (where ð represents
the Norse letter edh, pronounced like the th in this,
and the final r is nearly silent and not a separate syllable)"

"An actual name was, indeed, coined by Sir Garanhir, as Cariadoc
recounted. "Ostgardr" (properly spelled with a stroke through
the O and with the Norse lower-case thorn instead of a d, means
roughly "East Castle" or "East City". It is pronounced vaguely
like "OOST-garth(r)", with the final r nearly silent."

"The name is certainly registerable. 'Ormr' (the final r is silent) is
found on page 13 of one of our standard heraldic reference books, Geir
Bassi Haraldsson's _The Old Norse Name_."
- - -