If you're willing to toss a few bucks to some of the most awesome guys around, the guys behind
Astronomi-con offer a scenario CD on their site. 50 of the most inventive scenarios you'll find out there, plus pictures and table layouts.
Here's an old favourite:
Convoy Raid (from memory, may not be totally accurate):
Battlefield: Standard 6x4 table, light to moderate terrain cover, with a road running right through the middle (long way). Designed for 1500 point armies, for higher points games you may want to substitute more imposing vehicles for the convoy. (Falcons and War Walkers, Devilfish and Piranhas, Land Raiders and Dreadnoughts if you're feeling crazy...)
***Note that Outflank should probably be disallowed, as having squads appear in the midst of the convoy could be a real game breaker and the scenario wasn't designed for 5th edition rules.
Deployment: Deploy 1 HQ and 2 Troops choices in 8 inch by 4 foot deployment zones, on opposite edges at one end of the table. Remaining forces are held in reserve. At the other end, a convoy of 3 Chimeras and 2 Sentinels travelling down the road (Sentinel up front, Chimeras in middle, Sentinel brings up the rear). Each Chimera carries a supply crate. The convoy uses a third turn, separate from player turns (Convoy, Player 1, Player 2, Convoy, P1, P2...), and it moves straight down the road at combat speed, each vehicle firing at the nearest hostile (aka: either player's) unit (opposing player should make the shots). If the road is blocked (lead tank gets wrecked, for example), the convoy moves around it by the shortest possible distance and resumes its run for the opposite board edge.
Gameplay: Forget kill points, forget table quarters, forget claiming and contesting objectives... Your troops are low on food and ammo, you NEED those crates! Crates are obtained by killing the chimeras - when the tank is wrecked, the crate falls out the rear hatch. For every time penetrating hits are scored on the transports (and if the tank explodes), roll a D6 - on a roll of a one, the crate has been hit and destroyed.
Once you've cracked open the convoy, it's time to grab the crates. Anything can pick up and carry a crate, with the following requirements:
1> The model must have a hand/claw/manipulator/tentacle/whatever to carry the crate with. For example, Dreadnoughts with two gun arms can't grab a crate, Dreads with a DCCW can.
2> One crate per model! No monster characters on jump packs snatching all 3 and running away on their own, or similar. Say that they've got to leave one hand free to fight with, or something.
3> If your opponent's unit grabs a crate ahead of you, you'll have to either shoot the unit apart and grab the crate yourself, or pile in and chop it out of them in combat. You have to be prepared to defend the crates if you want to keep them!
Victory: It all comes down to posession of the crates at the end of the game. Whoever's got more, wins. If you bloodthirsty lunatics manage to blow up all the crates instead of grabbing them, it's an automatic draw - you can go right ahead and rampage however you want with the remainder of the game.