According to Official Guinness Records,
The largest dagger measured 91.50 cm (36.02 in) in length and 21.60 cm (8.50 in) at its widest point and was achieved by Oman Telecommunications Company (Omantel) in Muscat, Oman, on 12 November 2011. The dagger was produced as a gift to His Majesty Sultan Qaboos Bin Said, to celebrate his 40 years of accession. The dagger was a Khanja- a traditional Omani dagger and Oman's national symbol. The dagger was made from wood and silver, with ornate carvings and mouldings.
For a complete list of 2011 records, please visit 2011 Guinness Records in Oman.