For Kel Adon I usually use medium-fast tunes, not slow tunes. It's just a personal preference of mine. I feel like kel adon is the first thing people in the shul are singing since they woke up on shabbos morning so I have found that they're not usually in the slow song mood; unless of course you're in a shul where people are in that type of mood by about 9:00 am (such as aish kodesh in Woodmere). That being said you can use just about any tune for kel adon but here are some that I have previously used:
1. Shiru Lamelech (Always a great tune but I haven't used it in a while because it's overused nowadays.) MBD shiru lamelech
2. Shalom aleichem (the popular tune. I love using it)
3. Any fast carlebach tune such as od yeshoma (carlebach od yishoma), meheira hashem elokeinu, ata takum, yachad yachad (carlebach yachad (at about 1:50)), l'shana haba'a, shomrim hafkeid l'ircha (carlebach shomrim), etc...
4. Ashira L'hashem (I first heard this tune on MBD's kumzits CD. I don't know who originally wrote it: MBD ashira l'hashem)
5. k'chu imachem d'varim (Rabbi Brazil from Far Rockaway: Brazil kchu)
6. Puppa chassidishe keil adon (ahavas kedumim keil adon). I've never used this because noone knows it but if I ever daven for the amud in a chassidishe shul I'll try this one.
7. Eitan Katz's Shabbos Kodesh.