A few stick in the mind:
Druk Air the best, but limited destinations
I liked Aurigney last Easter
Virgin Blue (or whatever it was called 6 years ago) had a really good atmosphere
BA WT+ to Africa, but hate them on domestic LHR-ABZ as 50% of flights are delayed by 30 minutes or more
Gulf Air is OK cattle class if you're not expecting business class service
Most hated is Royal Nepal Airlines (OK, it was 13 years ago) with their advanced sleep deprivation techniques, probably honed for use in Guantanamo Bay
Easy jet do what they say, you save money and it's not as comfortable as BA or BMI, but you don't have to go to LHR, so that's a plus in my books