The ones already mentioned are all really good. Other faves of mine are walking from Lynmouth up the river to Watersmeet, then continue following the Coleridge Way as far as Ashton Cleave where you head up to County Gate. Cross the A39 and join the SWCP which you then follow back to Lynmouth.
That's a long day out around 12-13 miles.
If you don't have time for the full loop you can cut up to Countisbury from Watersmeet then join the coast path for a route of only 4.5 ish miles, you could add another couple of miles to that by walking down to the lighthouse at Foreland Point.
My other suggestion would be Badgeworthy Coombe from Malmsmead made famous as the setting for Lorna Doone. As you head up the Coombe the valley gets wilder then you return over open moorland on the bridleway over Manor Allotment and South common to Oare Church where Lorna is shot in the story when she is about to marry John Ridd. This walk shows the sort of route I mean
http://www.theaa.com/walks/down-the-doone-valley-420931 8.7miles, could be made shorter.