Cryptic Crossword Helpers

Trying to do American Cryptic Crosswords can occasionally require snippets of US pop culture that few Australians recognise, so I'm going to start collecting them here so that others I try to turn on to cryptics don't give up in despair.  This blog entry, more than any of my others, is likely to see edits as I encounter new references that need explaining:

letters	clued as
EL	Train, Railway	why?
OTT	Baseball player, Mel	why?
TY	Baseball player, Cobb	why?
A, A's	Baseball team, Oakland team	why?

And some, perhaps obvious, common clue indicators

clue	suggests
!	An exclamation mark usually means that the entire clue should be read two different ways, rather than looking to seperate it into two clauses
?	An question mark usually means that the wordplay in the answer may be even more groan-worthy in terms of punnishness.
Reverend Spooner	Two words will have their prefixes phonetically switched. To shout across the harbour might be a "Bay Hail" which is also clued as a "Hay Bale".	why?