Pretty much all of them have enough skillful moves, originality and charm to be worth watching over the majority of DBZ fights, though some particular highlights would be...
Kuririn VS Bacterian - Nothing major, though it at least having a basic display of brute force not being everything in a battle makes it a lot more entertaining than most of the fights after the Freeza Arc.
Goku VS Roshi - The fight constantly have the two changing tactics and fighting styles to counter their opponents and, as far as tournament arcs in Shonen go, has a subversive ending.
Goku VS Murasaki - One of the best gag fights in the series, aided by both fighters making good use of the battlefield to their advantage.
Taopaipai VS General Blue - Most badass kill in the entire series.
Goku (post-Karin) VS Taopaipai - One of the best stomp matches in the series, mainly since the training gains here actually meant something from the effort and new skills Goku learnt, unlike most of the power ups from the Freeza Arc and onwards.
Yamcha VS Mummy - A stomp match in the Mummy's favour, but it was at least made interesting by Yamcha using the terrain to his advantage, something you don't see in most later matches outside of Budokai ringouts.
Roshi VS Tenshinhan - Adding a lot of filler movements really aided this fight's choreography in the anime, with the right directing to display it's story significance.
Goku VS Tenshinhan (22nd TB) - Much like the Goku VS Roshi fight in how it was a constant case of matching each other's techniques, though on a far greater level.
Goku VS Young Piccolo Daimao - An even match filled with the right balance between hand to hand scuffles and over the top Ki blasts. What most of the later fights in DBZ should've been.
Goku VS Tenshinhan (23rd TB) - A very good demonstration of many of the philosophies Goku learnt in his training with Popo, such as not making unecessary movements, displaying his development as a fighter.
Goku VS Piccolo - Much like the match with Daimao. Whilst not as good overall due to how ridiculous both their durability became when withstanding each other's strongest amplified moves, it at least showed growth in that Piccolo had actually learnt from his mistakes, thereby making it a better rematch than most later ones in the series (*cough*FnF*cough*)