A long time ago i wrote up a space based rpg (I write/publish rpgs as a hobby) called Dead Orbit (yet to be released, i got lazy) with a few original aliens. Greys, Havaar, Reapers, and Tik'Ha and Serva
Obviously greys aren't original. As for the Havaar, my idea of them was basically the same as Ortnoks. The ones i am really going to mention are the three latter.
The Serva: Bipedal medium sized creatures that hunch over while keeping their weapon hand raised in the air menacingly. Their weapons are symbiotic creatures that latch onto their arms.
The serva are red skinned monsters with an array of bony spikes on their backs and several short tentacles where their mouth is, the tentacles grasp food and put it into their small mouth opening. There are three types of serva. The first wields a single symbiotic blade that has latched to its arm, this blade is large and bony. The second wields a creature latched to its arm that spits a glob of acidic saliva that breaks down biotic matter that it touches. Its less useful against metallic armor, but clothing and phalanx light armor is chewed through in less than a second. The last variety is a larger black version of the first type.
Tik'Ha: These insectile humanoids stand at 4" and their arms are a set of inherent blades that can cut through heavy armor in seconds. Their legs have a set of advanced glands that allow them to close distance with enemy's quickly. Though they are killing machines, they lack a brain, instead their thought are given to them by a nearby hive creature. The two types of hive creatures are praetors and queens. Praetors are double size as drones, have a extra set of blade arms, and have grown two acid spewing sacs in its mouth, allowing it to attack at distance.
The queen however... is usually big enough to climb up a new york skyscraper, and then its arm blades cut cut it in half, then it could push the section it cut off downwards and jump to another skyscraper. Four acid spewers, three sets of gigantic blade arms, 50" tall, weighs a good couple a hundred tons. Any PHALANX soldiers nightmare. Luckily queens are rare and only live inside the underground caves that the tik'ha call home.
And finally, the reapers: Reapers are rare, 10", purple skinned humanoids with only two large yellow eyes visable on their round hairless heads. Reapers are masters of staff combat, and are psionicly adept; and are as a result able to emit a mental barrier that can block just about anything. the disadvantage is that this barrier can be destroyed and takes a few hours to reassemble. The reaper wields a scythe and can jump up to ledges when he wants to. Reapers are usually only found in bases and on capitol ships. Even then only one will be present.
Any suggestions and feedback are apreciated