Bear ion mind Space Marines can still die, reading the background in the codexes and some of the fiction a marine can be brought down by a large enough gun, remember the phrase "give me a hundred marines failing that a thousand of anything else", so a group of ten guardsman should be an even fight for 1 Marine!

id give them stat lines of 40-49 across the board and between 15-20 wounds in the full power armour

and marines do have personalities but to those who arnt marines normally all they see is a stern face an bolter fire

Below are my implants from a larger document I put together last March. Let me know what you think.

1) Secondary Heart – the space marine gains the benefit of the Die Hard talent
2) Ossmodula – the imposing physique of the space marine and the hardened armoured bone result in two statisitical changes – first the space marine’s size is increased one step. Second, all primitive weapons used against the space marine treat his toughness bonus as modern armour, doubling it for purposes of resisting damage
3) Biscopea – the imposing musculature of the space marine is legendary. The space marines unarmed attacks and attacks with primitive weapons are not considered primitive. The hands of a space marine can crush the gorget of carpace armour as easily as grox-hide
4) Haemastamen – the space marine’s exertions are extraordinary. A space marine must accrue twice his toughness bonus in fatigue levels before losing consciousness from fatigue. The space marine also receives the benefit of the Hardy talent
5) Larraman’s Organ – the space marine only suffers the effects of blood loss for one round before the larraman cells stop his wounds
6) Catalepsan Node – the space marine is able to go four times the standard number of hours without sleep before incurring fatigue.
7) Preomnor – the space marine is able to derive nutrition from any organic substance he can force down his throat in small enough pieces. The space marine also gains the benefits of the Decadence trait.
8) Omophaega – any effects of the omophaega should be strictly narrated by the GM. Consider it a common knowledge check against the appropriate skill group after consuming the subject.
9) Multi-Lung – the space marine is able hold his breath four times as long before incurring fatigue in a hostile environment where oxygen is in some form available. This does not apply to strangulation
10) Occulobe – the space marine obtains the benefits of the Heightened Senses: Sight and Darksight talents.
11) Lyman’s ear – the space marine obtains the benefit of the Heightened Senses: Hearing talent and gains a +10 to all checks to keep his balance.
12) Sus-an Membrane – any suspended animation effects of this implant are purely at the GM’s discretion. Note that a space marine must be removed from this coma by outside forces. Activation of the Sus-an may be a one way trip to new character land if the GM is feeling nasty.
13) Melanochrome – the space marine incurs fatigue at one-quarter the rate of a normal human from any environmental effects such as sun, heat and radiation
14) Oolotic Kidney – the space marine obtains the benefits of the talent Resistance: Poisons.
15) Neuroglottis – the space marine obtains the benefits of the talent Heightened Sense: Taste.
16) Mucranoid - the space marine incurs fatigue at one-quarter the rate of a normal human from any environmental effects such as cold, wind and humidity.
17) Betcher’s Gland – the space marine may spit acid using BS or produce acid damage from a bite with WS. This acid does 1d10+TB damage and can ignore certain item armour values if the item is gnawed on over time. Generating the acid from a space marine’s Betcher’s gland is a “Ready” half action. The acid may be held in ready for as long as practical without damage to the space marine’s mouth. The acid may be swallowed without any harsh effects thanks to the preomnor.
18) Progenoid Glands – these are the space marine’s genetic destiny. His only truly lasting legacy within the chapter should he die. Improper respect for the progenoids can lead to dire consequences from the chapter’s apothecaries, chaplains and captains. The space marine gains the Chem Geld Trait without an insanity point.
19) The Black Carapace – the space marine is able to gain the benefits of the talent power armour training: space marine. Among the benefits, a space marine in power armour remains Hulking and does not increase in size to Enormous.