SELECT o.name AS FunctionName
FROM sys.objects AS o
LEFT OUTER JOIN sys.all_parameters AS p
ON o.[object_id] = p.[object_id]
WHERE o.type IN ('AF', 'FN', 'IF', 'TF')
AND p.parameter_id IS NULL
ORDER BY o.name
To find all stored procedures that have no parameters, use this code:
SELECT o.name AS ProcedureName
FROM sys.procedures AS o
LEFT OUTER JOIN sys.all_parameters AS p
ON o.[object_id] = p.[object_id]
WHERE 1 = 1
AND p.parameter_id IS NULL
ORDER BY o.name