5-seek version

SELECT
    FTC.Id,
    FTC.[Name],
    Fee =
        CASE
            WHEN EXISTS
            (
                SELECT TOP (1)
                    FT1.Fee
                FROM dbo.FeeTest AS FT1
                WITH (FORCESEEK)
                WHERE
                    FT1.ClientId = FTC.Id
                    AND FT1.Val <> 'Default'
                    AND FT1.Val2 <> 'Default'
            )
            THEN
            (
                SELECT TOP (1)
                    FT1.Fee
                FROM dbo.FeeTest AS FT1
                WITH (FORCESEEK)
                WHERE
                    FT1.ClientId = FTC.Id
                    AND FT1.Val <> 'Default'
                    AND FT1.Val2 <> 'Default'
            )
            WHEN EXISTS
            (
                SELECT TOP (1)
                    FT2.Fee
                FROM dbo.FeeTest AS FT2
                WITH (FORCESEEK)
                WHERE
                    FT2.ClientId = FTC.Id
                    AND FT2.Val = 'Default'
                    AND FT2.Val2 <> 'Default'
            )
            THEN
            (
                SELECT TOP (1)
                    FT2.Fee
                FROM dbo.FeeTest AS FT2
                WITH (FORCESEEK)
                WHERE
                    FT2.ClientId = FTC.Id
                    AND FT2.Val = 'Default'
                    AND FT2.Val2 <> 'Default'
            )
            ELSE
            (
                SELECT TOP (1)
                    FT3.Fee
                FROM dbo.FeeTest AS FT3
                WITH (FORCESEEK)
                WHERE
                    FT3.ClientId = FTC.Id
            )
        END
FROM dbo.FeeTestClient AS FTC;