The initial idioms of the letter A

be not half bad	not hold still for (something)
not playing with a full deck	be not worth a plug nickel
not worth writing home about	be nothing short of (something)
be nothing special	be nothing to shout about
be nothing (much) to write home about	be of like mind
be of no account	be of two minds
be of unsound mind	be off
be off base	be off beam
be off like a prom dress (in May)	be off (one's) chump
be off (one's) dot	be off (one's) nut
be off (one's) trolley	be off the beaten path
be off the (starting) blocks	be off the mark
be off the rails	be off the reservation
be off the table	be off the wall
be off-color	be off-kilter