Did you check the main smackdown thread?
In case, cleric archer ones are pretty simple. Use GMW on your bow and arrows. Have weapon focus, point blank, rapid and precise shot. Use bracers of Archery. Be hasted. Have a +4 Mighty Bow and use divine power and divine favor - persistent spell is nice.
The bonus to hit should be at least +50 (+20 base, +6 luck, +5 bow, +5 arrow, +1 focus, +2 comp, +1 point blank, and around +10 in dex). Therefore, attacks come in at +48/+48/+48/+43/+38/+33. Actually, a stored Tenser's Transformation would help, but I'll assume that the additional +6 or so doesn't matter. Dex could be higher as well. Remember to subtract 1 when beyond 30 ft.
Arrows will do 1d8+22 (+5 bow, +5 arrow, +6 luck, +4 strength, +1 comp, +1 point blank) when within 30 ft. A 20th level character will probably have a magic bow - let's make this one +1, Holy, Flaming and shocking. Against appropriate targets, that's another +14 on average. So that's about 240 if all hit, ignoring crits.
And I'm sure that could be improved.