Today is to show a model I finished a while ago, but it highlights a useful and cheap conversion which might help some Imperial Guard players out there.
Under 5th edition, taking two or even three Hydras was a common and competitive element of many Guard armies. Under 6th edition, the Hydra now has the Skyfire rule which has changed it's use considerably. The Hydra is now a dedicated anti-air and skimmer gun battery, and should only be used in extremis against ground targets (it can only make Snapshots). However, bear in mind that the autocannons are twin-linked which obviates the disadvantage of firing at BS1. The Hydra remains a solid anti-air choice, and is useful to armies without proper anti-air capacity as a an ally.
Whilst the Forgeworld Hydra is an excellent piece of kit, it is also expensive. I've never owned one, but there are many horror stories online about gun barrels being warped - fixable, I know, but annoying when you spend so much money on a model! So, I decided to make my own solution to the problem, and back when the Planetstrike terrain was released I instantly decided to convert my own Hydra... It's a simple conversion: mounting the Aegis Quad Gun on the turret socket of a Chimera! Of course, you can go further than that by creating a more specialised chasis - leaving off the "troop compartment" at the rear and adapting the chasis from there is an idea. I decided to keep things cheap and simple.