The Rumle is an awesome combat mount that features a huge shield and a siege mode.
Siege mode gives this mount a different ability set.
The direction you face on the mount also adjusts on your current target.
As you're mounted in Siege mode, you also build up a buff that makes you immune to CC for up to 8s when dismounting.
The animations on this mount are very smooth.
This mount can be upgraded with a reactor from the Mosiac Sale.
More info on upgrading can be found here.